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HomeMy WebLinkAboutPOTTS PUD PRELIMINARY - 6 92 - SUBMITTAL DOCUMENTS - ROUND 1 - TRAFFIC STUDY (2)00 M 0 00 O 0 O O v 0 Z g O J W D Z W a Z a r Z a m ui s C7 J W G -2 W x H F- Q .o r P 10 �9 cn 0 M �wir�tia-i �e.�tl�►� 2�1 2 MEMORANDUM ?A To: John Freeman, Architecture One Fort Collins Transportation Department Fort Collins Planning Department From: Matt Delich Date: February 7, 1992 Subject: Potts PUD traffic study (File: 9206MEMO) The Potts PUD consists of 26 two bedroom dwelling units proposed to be located south of the Taco Bell restaurant and Diamond Shamrock convenience store on West Elizabeth Street in Fort Collins. They are west of the Matador Apartments. Primary access to the Potts PUD will be via an existing driveway located between the Taco Bell restaurant and the Diamond Shamrock convenience store. A secondary access might be allowed through the Matador Apartments parking area. However, this traffic study assumed that all traffic would utilize the access to West Elizabeth Street. This memorandum specifically addresses the trip generation from the Potts PUD and the operation of the West Elizabeth access intersection. Peak hour traffic counts were obtained at the West Elizabeth/access intersection on January 29, 1992. Traffic counts were specifically taken after Colorado State University was in regular session. These counts are shown in Figure 1. Raw count data is provided in Appendix A. Table 1 shows the peak hour operation at the West Elizabeth/access intersection during the morning, noon, and afternoon peak hours. Calculation forms are provided in Appendix B. Based upon the 1985 Highway Capacity Manual technique for stop sign controlled intersections, the intersection operates acceptably, except for northbound left -turns during the noon and afternoon peak hours. At these times, the combination of background traffic on West Elizabeth and the northbound left turns from the access cause the operation to be at level of service E. By definition, acceptable operation is considered to be level of service D or better. Based upon recent research, it was found the 1985 HCM capacity technique for stop sign controlled intersections gives an overstatement of the level of service. The expected delay to the northbound left turns would be 18-28 seconds per approach vehicle during the noon peak hour and 17-27 seconds per approach vehicle during the afternoon peak hour. By other criteria also contained in the 1985 HCM, the level of service is more appropriately defined as level of service C/D. Appendix C contains copies of two research papers discussing this subject. Much of the data used in my research was Table 3 Peak Hour Operation with Existing plus Potts PUD Traffic Intersection W. Elizabeth/Access Driveway NB LT NB RT WB RT Level of Service 1985 Highway Capacity Manual AM NOON PM D (A/B/C)* E (C/D)* E (C/D)* A A A A A A * Operation considering the recent research and expected delay Table 4 Peak Hour Operation with 10 Percent Increase in Traffic Plus Potts PUD Traffic Intersection W. Elizabeth/Access Driveway NB LT NB RT WB RT Level of Service 1985 Highway Capacity Manual AM NOON PM D (A/B/C)* E (C/D)* E (C/D)* A A A A A A * Operation considering the recent research and expected delay APPENDIX A MATHEtN J. DELICH, P.E. 3413 BANYAN AVENUE LOVELAND, CO 80538 COUNTS TABULAR SUMMARY OFVEHICLE COUNTS 1 1 Z Q' 4 Z Day A/ GQ"'5 City l o1Z T COL L t N S R= Right turn Observer Date p S = Straight INTERSECTION OF A Cc fS5 70 I A c o EG�I(:A T AND. �G57 CG Ar3(-"?H L = Left turn Accc SS W.Ctr�A9&T9 (A). Gcr�AgT« c' TIME BEGINS fmm NORTH fmm SOUTH TOTAL North fEAST mm from WEST TOEast TAL TOTAL ALL R S I L Total R S L I Total South R S I L I Total West II R S L I Total 44 730 I to I I I 1 II 1 Izs I I IZG 41►3o1 I►34 [(DO 1 1(a 7¢s� II I I z 14 1 6,II p 12& s 1 31 11 3 lzjj I 1 22 2 lIZ53 11 Z s9 I I I Iz z 1 4- II 4- 11 144 14 14s II 31 971 I100 1114 II 1 G7- 115-1 1 1 1 II G II 1381 1 1 39 113 951 1 9.8 /37 II 14-3 I I I I II I I I II I I IIpMF=o.lo41 I I I I q 15s 11'1 II r I 113.3111 114411315211 15 ,d11&9 2 117 1 rzoo l I I 111(o1 1,91 35 11 36- 11 I1Zo 1S41 as4 1 j3 1 lo7I I /zoll Z7411 30 1ZlS 1131 1 11-4.1 43 II 43 13(013Z 1/ cg I f9 Ito41 I 1 z -3-11 19 1' 11 334 123OI I I I 13571 1Z3 s� 11 -'7 I I'64131 f 16-11301to2 1137- Z 7 1130S- )aasI I 52I NP14-3 11 4-9 11 1'i3 Z91t-/.Z 11to I Is 113 ZSI zq9 I I I I II I I II I I I II I I 1z�F=o.93 I I I I 111141 I oft A- 11 1 S 4 11 14Z3112b1s49117Co143 I IS--1 4 11 1o(o3111247 43o II I I I 115-1 114 1 1 q II 1 9 11 114711q 116Co Ills /oq I Ilz¢ I Zoo 11301 4-45 I 11131 11(0 1 z 9 11 z *► II I IGO 1 191 l -711 1112 1Z5 1 11 37 3 1& 134 S �av I I I 119 1 1 q 1 13 11 1cC 1 1133 1111411115- I-zZ1 1137 Z13Co 11364 1 I I I /& 1 12 I z4 11 4. S-1 I 1(o1 17s 11 /Z 110g l II Z I z91'o 113Zo 1A31 I4-1 1 9011 q 11 1l 04I &51 &c,, 9116.4I 4(o5l I s-1 g 11 11?? 11 1Z71' APPENDIX B 1985 HCM: UNSIGNALIZED INTERSECTIONS Paoe-1 Y MYMZ#ZYZMZ#ZYZ1:#YYXMYMKMZZMMYKYYMYXZ ZX.Y YYMZMMYYXYZMYMMXM#Y.:KMKY.KMMMYZ IDENTIFYING INFORMATION ------------------------------------------ ------------------------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .69 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am noon pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- E6 W6 NB SB ---- ---- ---- ---- LEFT 0 11 6 -- THRU 541 133 0 -- RIGHT 13 0 9 -- NUMBER OF LANES --------------------------------------------------------------------- EB WE, NE S8. -------------- ------- ------- LANES 2 2 -- CAPACITY AND LEVEL -OF -SERVICE Page-3 --------------------------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH ------- -------- --------------------- ------------ --- MINOR STREET .3zr NB LEFT 13 189 185 185 172 D RIGHT 14 699 699 699 685 A MAJOR STREET WB LEFT 18 424 424 424 406 A IDENTIFYING INFORMATION NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS..... 2/3/92 ; am noon pm OTHER INFORMATION.... 19 with dev sensitivity 1985 HCM: UNSIGNALIZED INTERSECTIONS Page-1 YXY.T#############it#####XXXL########XL#Y###Y##YiY#xYz#######Y###### IDENTIFYING INFORMATION ---------- --------------------------------------------------------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .93 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am moon pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- EB WB NS SB ---- ---- ---- ---- LEFT 0 126 70 -- THRU 438 423 0 -- RIGHT 76 0 114 -- NUMBER OF LANES --------------------------------------------------------------------- EB WB NB SE, ------- ------- ------- ------- LANES 2 _ -- CAPACITY AND LEVEL -OF -SERVICE Page-3 --------------------------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH --------------- --------------------------------- --- MINOR STREET IB_Z B' S« NB LEFT 83 164 134 134 52 E RIGHT 135 814 814 814 679 A MAJOR STREET WB LEFT 149 589 589 589 440 A IDENTIFYING INFORMATION ------------------------------------------------- NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS..... 2/3/92 : am noon pm OTHER INFORMATION.... 1992 with dev sensitive y 1985 HCM:. UNSIGNALIZED INTERSECTIONS Page-1 s sssssssssssssssssscssssxssssssssxsssssssssssssssssssssssssssssssssss IDENTIFYING INFORMATION ---------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .93 AREA POPULA.TION...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mjd DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am noon pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- EB WB NB Sp. ---- ---- ---- ---- LEFT 0 65 d7 -- THRU 465 604 0 -- RIGHT 54 0 4;, -- NUMBER OF LANES --------------- ES WE, NB SB ---------------------------- LANES 2 _ 2 -- CAPACITY AND LEVEL -OF -SERVICE --------------------------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY v(pcph) c (pcph) c (pcph) c (pcph) c= c - v LOS p M SH R SH ------- -------- --------- ------------ ------------ --- f_Zl sec• 56 132 120 120 65 E 51 811 811 811 760 A. MOVEMENT MINOR STREET NB -LEFT RIGHT MAJOR STREET WB LEFT Page-3 77 585 585 585 509 A IDENTIFYING INFORMATION ------------------------------------------------------- NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANA YSIS..... 2/3/92 : am noon pm OTHER INFORMATION.... 1992 with dev sensitivity APPENDIX C - - ... ... ._..._.- . INTI'IZMC)tJNTAIN SI:C TION --- _..------ -- --.-- ----- DOISE, IDAfIU "_.._. _-_.__. _.......__ __...._ .. _.—DULY 15_18,-1990 Compendium of Technical Papers Institute Of Transportation Engineers 43rd Annual Meeting Boise, Idaho July 15-10, 1990 Intersection Delay At Unsignalized Intersections Matthew J. Delich, P.E. Private Consultant Loveland, Colorado ARSTRACI' The technique described in the llighway Capij tjty Manual, Special Report 209, Chapter 10, Unsignalized Intersections relates it calcu- lated reserve capacity to level of service to it very unspecific description of expected delay. The signalized intersection technique in the highway Capacity Manual relates level of service to a range of stopped delay per vehicle. It would seem to be consistent to relate level of service at an unsignalizcd intersection to it range of actual delay per approach vehicle. This research provides some limited data on intersection delay related to the calculated reserve capacity at selected T'-intersections. At the lime traffic volumes were collected, infer - section delays were also obtained for selected movements. The intersection delay technique is described in the Manual of Traffic Engineer- ing Studies, IT'E, 1976, Chapter S. By compar- ing the calculated reserve capacity using the counted traffic volumes to the observed aver- age delay per approach vehicle, a table of delays per approach vehicle could be deter- mined. This, in turn, could be plotted to determine a range of delay given a calculated level of service. INTRODUCTION The means of evaluating the operation at an unsignalized intersection is by determining the level of service. The procedure in the 1995 Highway Capacity Manual (I ICM) is primarily 145 taken from a German document (reference 1), which uses gaps in the major traffic slrcam utilized by vehicles crossing or turning through that stream. In the IlCm, the level of scl vice is rclalcd to vehicle delay. This is especially true in file evaluation ill it signalized iulcrscclion. 1lowev- cr, in the case of an unsignalizcd inlciseclion, level of service is rclalcd to it nebulous mca- sure of delay that can mean different things to different people. RESEARCII OII,11sC1'IVES This research was undertaken to relate level of service to it definitive range of vehicle delay for the minor street traffic flow. The objec- tives of the research were: 1. Compare the level of service (reserve capacity) to a range of vehicle delay, in seconds, for the stopped traffic on the minor street. 2. Determine a curve which best de- scribes that range of vehicle delay. RESEARCH APPROACH AND LIMITA- TIONS Traffic counts were conducled al it number of slop sign controlled intersections in Foal Collins, Colorado and Cheyenne, Wyoming. These volumes were used to dcicrmine reserve capacity in passenger tams per hour (pcph) p .r obtained in Fort Collins and, therefore, reflects local driving characteristics. The basic conclusions of my research is supported by a similar study conducted in Boston, Massachusetts. During traffic counting, it was observed that delays to the northbound left turns were as little as 2-3 seconds and as much as 30-35 seconds. This observation supports the expected delay range stated earlier. The large difference in observed delay was due to the release of vehicles at the Taft Hill/Elizabeth signalized intersection to the west, and the Elizabeth/City Park intersection to the east. These signals create vehicle queues which caused some extended delay. Conversely, the queues caused some long gaps in the traffic stream on West Elizabeth which allowed some vehicles to make left turns with virtually no delay. It is my conclusion that the level of service E shown in Table 1 should be tempered when considering the additional information provided above. In my judgment, the northbound left -turn exits from this access are in the level of service C/D category. Trip generation is important in considering the impact of a development such as this upon the existing street system. A compilation of trip generation information, prepared by the Institute of Transportation Engineers dated 1987, was used to project trips that would be generated by the proposed residential use. This information was supplemented with data contained in Urban Travel Patterns for Hospitals, Universities, Office Buildings, and Capitals, NCHRP Report 62, HRB 1969, since the residents of this development are expected to be predominantly college students. Table 2 shows the trip generation expected from this development. The trips for the Potts PUD were divided into two categories: school (CSU) and non -school trips. The non -school trips can be categorized as work trips, shopping trips, recreation trips, etc. Using the apartment use from Trip Generation, 4th Edition to determine the trip rates, it was assumed that 20 percent of the peak hour trips would be non -school trips. This is shown in the row labelled non -school trips in Table 2. Using the information contained in NCHRP Report 62, the number of peak hour school person trips was determined. This is shown in the row labelled school person trips in Table 2. Based upon the location of Potts PUD with regard to CSU, it was assumed that half of the school person trips would be by modes not involving a personal motor vehicle. These modes are Transfort, walk, or bicycle. Transfort operates on West Elizabeth Street. West Elizabeth Street is also a significant bicycle route to CSU. The geographical center of CSU is less than one mile from the Potts PUD. This makes pedestrian and bicycle travel an attractive travel alternative. The number of school motor vehicle trips is considered to be conservatively high. These trips are also shown in Table 2. Two directional distributions of the generated trips were determined for the Potts PUD development. The distribution for the non -school trips used employment as the attraction variable in the gravity model. School related vehicle trips for Potts PUD were oriented toward CSU. Both trip distributions are shown in Figure 2. Intersection Delay At Unsignalized Intersections according to procedures documented in the 11CM. Ilighway capacity software developed by the; Federal Highway Administration, U.S.- D.O.T. was used to perform diese calculations. Along with the Iralfic volumes, vehicle delay was nicasurel for each approach vehicle according to procedures described in Chapter 8,. "Intci:seclion Delays," Mamial of Tral;lic 1:ftinccring Stiidict. Due to changes in critical gap size due to speed, number of lanes on the major sued(, and number of Icgs al the intersection, only T- inlcr:eections were evaluated. Further, in all cases, the major street was five lanes (4 through lams mid one, left-Iurn little) and the speed limit on file major street was 35 mph. IN17?RSI?CHON DI I.AV STUDY At the time traffic volumes were obtained tit each of the inteiseclions, traffic delays were also obtained for both right- and left -turning vehicles from the minor street. The methodol- ogy used was it procedure which involved counting the number of vehicles occupying an intersection approach (right- or left -turn lanes constitute two approaches) at successive time intervals for the observation period. 1 he successive time interval selected was every 15 seconds. Each successive count represented an instantaneous density or number of vehicles occupying the intersection approach per time interval. These counts were accompanied by total volume counts of each approach. The average delay per vehicle in each approach can be expressed by: 1)=NIN where: 1) = Average delay per approach vehicle N = Total density counl, or the Burn of vehi- cles obseived during the per iodic density counts each I seconds t = Tillie intervals between density obsctva- tions (15 seconds) 146 V = Total volume entering the ap- proach during the study period. A total of 61 fifteen minute observations were conducted. The average delay per approach vehicle for both right and left turns for each observation was tabulated. The calculated delays were rounded to the nearest whole second. The calculated delay per approach vehicle for right turns ranged from 2 seconds to 29 seconds. The mean was calculated at 9.9 seconds. The calculated delay per approach vehicle for leh turns ranged lion) 6 seconds to 105 seconds. The mean was calculated at 27.0 seconds. L EVIsL OF SERVIUU, CALCULATION Using file same 15 minute periods from the intersection delay study portion of this re- search, level of service calculations were per- formed. Since the level of service calculation requires hourly traffic, the volumes for each 15 minute period was factored by four. This not only gives an hourly volume, but also assumes a peak hour factor of 1.0. Reserve capacity in passenger cars per hour (pcph) was tabulated for the right turns and left turns for each observation. The calculated reserve capacities ranged from 36 to 882 pcph for the right turns. 1'Iie mean was calculated at 565.5 pcph. Most of the calculated levels of service were in the A category (> 400 pcph). 11ie calculated reserve capacities ranged from - 75 to 241 pcph for the left turns. The mean was calculated tit 66.9 pcph. Most of the calculated levels of service were in the D category (100-200 pcph), E category (0-100 pcph), and F category (< 0 pcph). ANALYSIS Using the output data for right turns and left turns from the delay study and the capacity study, each corresponding observation point was plotted and least squares graphical analysis was performed. Figure 1 shows the plot of calculated reserve capacity versus calculated delay per approach vehicle for the right turns. The results of the graphical analysis are also plotted. By calculat- ing confidence interval as a range of delay per approach for each calculated reserve capacity, a reasonable prediction of delay can be made. For example, a calculated reserve capacity of 400 pcph would yield a delay per right -turn approach vehicle of 10-15 seconds. Figure 2 shows the plot of calculated reserve capacity versus calculated delay per approach vehicle for left turns. The results of the graphical analysis tiro also plotted. Using the confidence interval, a prediction of the range of delay can be made. llowevcr, the data for the left turns is all in the -100 to -1-2W nu►ge of values. Therefore, the delay for left turns is only valid for reserve capacities tit the lower end of the scale using the data considered in this 'study. For example, a calculated reserve capacity of 100 pcph would yield a delay per left -turn approach vehicle of 12-22 seconds. The size of this range indicates that more data is needed to reduce the prediction range. CONCLUSIONS Given the limited data obtained (61 observa- tions), it appears as though the methodology can give a reasonable indication of the range of delay for vehicles entering a street at a stop sign controlled T-intersection. however, more data is needed to fill in gaps: 1. Data is needed at intersections where the right turns operate at levels of service B, C, I), E. 2. Data is needed at inlcrseclions where the left turns operate at levels of ser- vice A, B, C. At a number of the analyzed intersections, there were signals upstream from the analyzed intersections. Some of these signals were as 147 District 6 1990 Annual Meeting close as 1/4 mile away. There was no signal progression pattern on ti►e major street. However, it was noticed Ihat both operation and delay were influenced by vehicle queues created by the signals on (lie main street. This was not accounted for in any of the calcula- tions or analyses. An effort should be made to select intersections which are not affected by main street signals. The statistical analysis on this data and addi- tional data should be uwch more rigorous than that used in this analysis. The curves devel- oped using nil the data should be malhc►uad- cally derived and ade(luately tested using acceplcd statistical praclit•cs. 'flee data presented is only for 11 T-intersection with a four -lane (plus left -turn lure) main street with it posted speed of 35 n►ph. Data should also be collected nl a number of stain street posted speeds (45 inph and 55 mph). Data should also be collected for a T-intcrsec- lion on a Iwo -lane sl►ccl at various posted speed limits. If the additional data and analyses for a T- inlersection point toward the validity of this approach, then similar data should be collected and analyses perforn►ed at four - leg intersections. BIBLIOGRAPHY Box, Paul 1). and Joscph C. Oppenlander, 1110. Manual. of Traffic Iinbinccring Studies, 41h lEdition. Arlington, Virginia: InstiUale of Transportation Engineers, 1976, Pgs. 106-112. Rocss, Roger P. cl al. I Iighw_iY C tlricily Manual, Special Report 209. Washinl,lon, D.C.: Transportation Ilcsca►ch hoard, 1985, Chapler 10. REFERENCE I. "Mcrkblatl for Lichlsignalanlagen an Land- alrassenAusgabe 1972", I-'►►rschungsgescllschaft Intersection Delay At Unsignalized Intersections fur das Strasscnwcscn, Koln, Germany (1972). 149 50-1- 45- 4o- 1 36- District 6 1000 Annual Meeting 01 11 01 op 01 11 01 01 01 1 01 OF 10 01 11 1 > 0 .4 01 e 'o 'o 960 Boo 700 660 500 400 300 200 100 0 RESERVE CAPACITY IPCPhI COMPARISON OF RESERVE CAPACITY AND DELAY FOR RIGIIT TURNS AT A T-INTERSECTION 149 Figure I I Intersection Delay At Unsignallzed Intersections 11 Bo 1- 40 6 Se- B • .r r.r r , r r r n ! • ..• J_.L.. • 0. 1 rtt-' T I- _ .. 1 1 Boo Boo too 000 Boo 400 Soo 200 100 f- 0 - nESEAY@ CAPACITY (peph) COMPAt11SON Of' nuimvE CAPACITY AM) VELAY FOn LEFT 1UIINS AT A T-IN1E"SEC'IION Figute 2 150 1-1 A METHODOLOGY FOR USING DELAY STUDY DATA TO ESTIMATE THE EXISTING AND FUTURE LEVEL OF SERVICE AT UNSIGNALIZED INTERSECTIONS By Marni Heffron (A)a and Georgy Bezkorovainy (M)b INTRODUCTION The level of service at unsignalized intersections is often overstated by the 1985 Nlghway Capacity Nanual (HCM) methodology. The HCH analysis for unsignalized intersections may show a LOS E or LOS F operation with lengthy delays and, presumably, long queues. However, from field observation, the intersection functions relatively well with short queues and minor delays on the approaches controlled by STOP signs and no delays to mainline traffic. Many reviewing -agencies require the use of the HCH methodology to determine level of service. However, ITCH states that "because the methodologies [for calculating unsignalized level of service) result in a qualitative evaluation of delay, it is also recommended, if possible, that some delay data be collected. This will allow for a better quantification and description of existing operating conditions at the location under study." HCH does not, however, include a methodology to relate delay study results for an unsignalized intersection with a level of service designation. ITCH defines the level of service of an unsignalized intersection using "reserve capacity", an analytically -defined variable that is not easily field -verified. The procedure is based on the German method of capacity determination at rural intersections. This method has not been extensively validated or calibrated for U.S. conditions, nor does it estimate delay in quantitative terms.11 This paper presents a methodology to use delay study data to determine the existing level of service and to estimate future operating conditions at unsignalized intersections. In developing the methodology, delay studies were performed at more than 50 unsignalized T-intersections in eastern and central Massachusetts. Minor approaches of these intersections were controlled by stop signs, yield signs and uncontrolled (implied yield). The results of these delay studies will also be compared to the delay calculated using the HCH unsignalized intersection analysis. This paper relies on the existing HCH methodology as the basis to estimate existing and future level of service from delay data. Until changes are made in the HCH procedure, the existing HCM methodology for unsignalized intersections will continue to be modified to yield results that better approximate existing and future conditions. a Transportation Engineer Bruce Campbell 6 Associates, Boston MA b Vice President Bruce Campbell 6 Associates, Boston MA UNSIGNALIZED INTERSECTION DELAY Delay was adopted as a measure of effectiveness for signalized intersections in the 1985 HCH for many reasons; two reasons are that the concept of delay is understood by the user community and delay can be measured in the field.3 The application of delay for unsignalized intersections should follow this same reasoning. The.,,reserve capacity is related to average vehicle delay using the following equation from the ITE Handbook2: d — 1 (1) (a - b) d — average delay a — service rate b — side -street arrival rate Recognizing that capacity is the service rate and volume is the arrival rate at an unsignalized intersection, this formula shows that the average vehicle delay is the reciprocal of reserve capacity. The average seconds of delay per vehicle is calculated using the following equation: Average Delay (Bee/veh) - 3600 (set/hr) (2) Reserve Capacity (veh/hr) Table 1 shows the level of service designations which correspond to reserve capacity and average vehicle delay. Because the average delay per vehicle approaches infinity as the reserve capacity goes to zero, LOS F will be defined by any delay over 60 seconds. The average delay values for unsignalized intersections shown in Table 1 are very similar to the delay values used to define the level of service of signalized intersections. Table 1 is taken from Table 10-3 in the HCH. Table 1 Level -of -Service Criteria For Unsignalized Intersections Average ** Level of Reserve Capacity Stopped Delay Service (pass Cars Per Hour) (sec/veh) A > 400 < 9.0 B 300 - 399 9.1 to 12.0 C 200 - 299 12.1 to 18.0 -D 100 - 199 18.1 to 36.0 E 0 - 99 36.1 to 60.0 F * > 60.0 * Demand exceeds capacity; extreme delays will be encountered ** Calculated from Equation (2) —1— MEASURED DELAY VS CALCULATED Y Delay studies at unsignalized intersections are relatively easy to perform and can be performed in conjunction with a turning movement count at low volume intersections. The observer measures the time between when a vehicle stops for a stop sign or �. conflicting traffic and pulls onto the major street. ,J The measurement includes the time waiting in queue. 13 The. stopped delay is measured for random vehicles 11 turning left or right from the minor street or turning t left from the major street. The average delay during the peak hour is calculated using a modified signalized intersection delay equation: Average Delay (sec/veh) . Total Delay (sec) (3) Number of Observations For locations with a shared lane for left and right turns on the minor street, the stopped delay for each movement should be kept separate if future conditions will be projected from the data since the level of service of each movement is calculated separately and then combined as a shared lane movement. Special consideration, discussed later, should be given to shared lane approaches where the right turn delay will be increased by a high left turn volume. The existing level of service for the shared lane is the weighted average of the combined movements. Bruce Campbell 6 Associates performed delay studies at more than 50 unsignalized intersections in eastern and central Massachusetts. For all study locations, a traffic count was also performed, and the level of service was calculated using the HCH methodology. To date, only a few delay studies have been performed at 4-legged intersections, so only the data for T-intersections are included in this paper. The average delay per vehicle was calculated using equation (3). Figures 1 through 3 compare the results of the measured delay and the calculated delay. The curves are from regression equations relating conflicting flow and average delay. At this point there have been no attempts to correlate the delay - data to another variable such as speed, movement demand or type of control. For all three critical movements at an unsignalized intersection --the left turn from the minor street, right turn from the minor street and left turn .from the major street --the measured delay was found to be shorter than the calculated delay. These data suggest. that drivers are selecting smaller gaps than those recommended in the 1965 HCH. Using the methodology described below to back -calculate to the critical gap, it was found that at over 80 percent of the locations, the critical gap for both the minor left and right turn movements was less than 6.0 seconds. It was originally suspected that the smaller gap size determined for the study locations would result in higher accidents rates at these locations. However, most of the intersections studied had accident rates less than 0.5 Acc/Million Entering Vehicles, and none had accident rates over 2.0 Acc/HEV. In Massachusetts, intersections with an accident rate of less than 2.0 are not considered high accident locations. FIGURE ) CON17LIC11142 FLOW VS. AVERAGE DELAY i ar, ,i ou, ariu,.AAitsR f1fFFF 0 0.2 v.. IThousendo) CONFLICT NaG FLOW . FIGURE 2 CONFLICTING FLOW VS. AVERAGE DELAY LEFT ,URN (ROM MBJOR 51REE1 CCN4rUC1tVG FLOW . FIGURE 3 CONFLICTING FLOW VS. AVERAGE DELAY RR:211 TURN IROM MINOR 51REET '_tAi MEn5�E0 o.. v.e •.e (Thousands) COMlICIM FLOW Intersections with a shared lane on the minor approach provided conflicting results for the left and right turn movements. In many cases, the critical gap determined from the delay data for the right turn was higher than the gap determined for the minor left turn. This phenomenon is most likely due to the time a right turner spends waiting in queue behind a left turner. Because of the queue, the measured delays for the two movements were not dramatically different. Since the critical gap calculation relies on the movement's conflicting flow, the right turn gap calculates to a higher value then the left turn gap. Generally, the minor left turn is the most critical movement at an intersection, and the delay data for the left turn is not significantly affected by a shared lane. In retrospect, if delay data measurements did not include stopped delays in a queue, then the calculated gaps would be higher for left turns than right turns in all instances. However, not recording delays in a queue would give an unfair representation of existing field conditions. To further illustrate the shared lane phenomenon affecting right -turning vehicles, the results in Figures 1 and 2 show a large disparity between the calculated delays vs. measured delays. However, in the case of right -turning vehicles, the measured delays were only 2-3 seconds less than the calculated delays. The presence of left -turning vehicles in the shared lane had, most likely, a significant impact on the delay values recorded for right -turning vehicles. Further research on shared -lane approaches is needed. ESTIMATING FUTURE LEVEL OF SERVICE The following procedure is suggested to estimate future level of service from existing delay data. It relies on the existing HCM methodology, and basically back -calculates from delay to capacity to determine the gap being accepted by drivers. Once the gap is determined, the future capacity and level of service can be estimated using the same gap. The capacity for an unsignalized intersection movement can be determined from delay -by rearranging equation (2) as follows: capacity (veh/hr) - 3600 (sec/hr) . Side Street Demand (4) Average Delay (sec/veh) The HCN equations relate critical gap to "potential capacity." The potential capacity for the. left turn from the major street and right turn from the minor street are the same as capacity, but the capacity of the minor left turn needs to be converted to potential capacity discounting the impedance factor of the major left turn. The impedance factor is determined using the following equation (the variable names correspond to the variables in HCM): r V l 1.2052 C(5) I — 1 - 0.0038 100 x 4 J p4 I — Impedance Factor V4 — Left turn volume from major street Cp4 — Capacity of left turn from major street The potential capacity of the minor left turn is then calculated using: ( Cm7 6) Cp7 — I C 7 — Potential capacity of the minor left turn Cm7 — Actual capacity of the minor left turn (determined from delay data) Using Figure 10-3 in the 1985 HCM, the critical gap can be estimated from the potential capacity and conflicting flow. Alternatively, the equations in Karsten G. Baass' article "The Potential Capacity of Unsignalized Intersections" (ITE Journal, October 1987, pp. 43-46.) can be used to determine the gap. The estimated critical gap may be lower than 4.0 seconds for low volume locations, but it is recommended that 4.0 be the minimum gap used. HCM's Figure 10-3 alsoashows the minimum critical gap to be 4.0 seconds. Once the critical gap is estimated from the delay data, the future level of service at a location is determined using the standard BCM methodology. This methodology is not recommended for intersections with high accident experience, or where vehicles on the side street are forcing a gap in the major street traffic stream. The following is an example of this methodology's application: EXAMPLE: A delay study and turning movement count were performed at the T-intersection of Lincoln Avenue and Bristow Street in Saugus, Massachusetts, The PM peak hour turning movement volumes and vehicle delays are summarized below: Average Peek Hour Conflicting Delay per Maximum _Sample Movement volume Flow Vehicle Delay Sire Minor Left 107 1227 13.7 64 92 Minor Right 33 653 5.4 28 31 Major Left 36 653 3.8 14 15 According to the HCM methodology, the left turn from Bristow Street to Lincoln Avenue operates at LGS F. The delay study data, however, show that the left turn operates at LOS C. The capacity of each movement is calculated using equation (4). Movement Demand Capacity Minor Left 107 vph 370 vph Minor Right 33 760 Major Left 36 983 The potential capacity of the minor left turn is calculated using the impedance factor from equation (5). The impedance factor is determined from the demand and capacity of the major left turn, I — 1 - 0.0038(100 x 3�)1.2052 _ 0.98 983 and potential capacity, Cp7 — 370 — 378 vph 0.98 -3- The conflicting flow of the minor left turn — 1227 vph. Using Figure 10-3 in the HCM, a critical gap of approximately 4.5 seconds is located for a potential capacity of 378 and a conflicting flow of 1227. These steps are illustrated in the flow chart in Figure 4. Under the future conditions, the conflicting flow is estimated to increase to 1400 vph, and the minor left turn demand will increase to 170 vph. The future potential capacity located on Figure 10-3 is 300 vph for a gap of 4.5 seconds and conflicting flow of 1400 vph. The actual capacity accounts for the impedance factor (for this example the impedance factor is assumed to be 0.98). Cm7 — 300 x 0.98 — 294 vph The reserve capacity — 294 - 170 — 124 vph, and the average delay is calculated using equation (2), Delay — 60 — 29.0 sec. 124 The level of service for the future conditions will be LOS D. CONCLUSION The methodology presented in this paper provides one way to quantify the operation of an unsignalized inter- section when the HCM methodology does not correlate with field observations. Future operating conditions can also be defined on the basis of existing conditions delay data. The delay methodology should not be used for intersections with high accident experience or where vehicles on the side street are forcing a gap in the major street traffic stream. Further research is needed for intersections with a shared lane on the minor approach since the right turn delay is affected by the left turn movement. Data collected for the left turn movement on a shared lane approach should not be significantly affected. Delay is a measure of effectiveness that should be applied to unsignalized intersections because it is easily measured and. also easily understood. Future revisions of the HCM methodology should include delay. REFERENCES 1. Transportation Research Board, National Research Council. "Research Problem Statements: Highway Capacity-, Transporation Research Circular Number 319. Washington D.C., June 1987, page 27. 2. Institute of Transporation Engineers. Transporation and Traffic Engineering Handbook. Prentiss Hall Inc.; 1987, pp. 499-536. FIGURE 4 ESTIMATING FUTURE LOS FLOW CHART Existing Future Conditions Conditions Measure Future LOS Delays Table 1 Avg. Delay I I Avg. Delay Per Vehicle Per Vehicle Equation (3) Equation (2) Capacity <f) I I Reserve Cap. Movement Subtract' Equation 4 Demand Impedance Actual Factor Capacity Equation (5) I Equation (6) Potential Potential Capacity Capacity from Equation (6) 1 HCM Fig. 10-3 Critical Gap Assume Same HCM Fig. Critical Cap 10-3 for Future 4. Baass, Karsten C. "The Potential Capacity of Unsignalized Intersections", ITE Journal, October, 1987, pp. 43-46. 3. Roess, Roger P. and McShane, William R. "Changing Concepts of Level of Service in the 1985 Highway 5. Transportation Research Board, National Research Capacity Manual: Some Examples," ITE Journal, May Council. Highway Capacity Manual, Special Report 1987, pp 27 31 209. Washington D.C., 1985. —4— v APPENDIX D Available peak hour traffic counts in this area of West Elizabeth Street from 1985 and 1988 indicate that traffic has generally stabilized in this area. The afternoon peak hour traffic has actually decreased by 20 percent since 1985. It is concluded that background traffic could be increased by 10 percent to indicate a modest growth, commensurate with the traffic volumes over the past seven years. Two future projections were made. Figure 3 shows the existing counted peak hour traffic with the Potts PUD generated trips. Figure 4 shows the existing background peak hour traffic factored by 10 percent with the Potts PUD generated trips. Using the traffic volumes shown in Figure 3, the West Elizabeth/access intersection will operate as indicated in Table 3. Calculation forms are provided in Appendix D. As with the existing traffic, the left -turn exits from the access will operate at level of service E during the noon and afternoon peak hours using the 1985 HCM technique. Applying the research discussed earlier shows that, in the noon peak hour, the delay to the left - turn exits will be. 18-28 seconds per approach vehicle and, in the afternoon peak hour, the delay to the left -turn exits will be 17- 27 seconds per approach vehicle. This is the same as exists today without the proposed development. The level of service of these movements wouldbe more 'appropriately defined as in the C/D category. Using the traffic volumes shown in Figure 4, the West Elizabeth/access intersection will operate'as indicated in Table 4. Calculation forms are provided in Appendix E. The northbound left -turn exits from the access will operate at level of service E during the noon and afternoon peak hours using the 1985 HCM technique. Applying the research shows that the delay to the left - turn exits will be 19-29 seconds approach vehicle in the noon peak hour and 17-27 seconds per approach vehicle in the afternoon peak hour. Even with the 10 percent increase in background traffic on West Elizabeth Street, operation will not be significantly worse than exists today. The movements that are calculated as level of service E are more appropriately defined as level of service C/D. operational level of service at the West Elizabeth/access intersection is acceptable with the Potts PUD traffic. During traffic counting, it was noted that the painted markings on the access driveway were worn off. There are faint indications of one southbound ingress lane and two northbound egress lanes (1 right - turn lane and 1 left -turn lane). The throat of the access is narrow. From available drawings, it scales 34 feet. This would indicate three lanes of just over 11 feet each. It was observed that on occasion both left- and right -turning vehicles positioned themselves so that the other exit lane was not usable by other exiting vehicles. This could be caused by either not well-defined pavement markings or a feeling of discomfort with the width of the driveway. There is only enough storage available for two vehicles before one access to the Diamond Shamrock convenience store is 1985 HCM: UNSIGNALIZED INTERSECTIONS Page-1 IDENTIFYING INFORMATION ----------------------------------- ------------------------------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .69 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. (am noon pm OTHER INFORMATION.... 199E with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------- --------------------------- EB WB NB SB ---- ---- ---- ---- LEFT 0 1$ 9 -- THRU 541 133 0 -- RIGHT 13 0 18 -- NUMBER OF LANES -------------------------------------------------- ------------------- EB WB NB SB ------- -------------- ------- LANES 2 2 -- CAPACITY AND LEVEL -OF -SERVICE Page-3 --------------------------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH ------- -------- --------- ------------ ------------ --- MINOR STREET &-I& gec NS LEFT 14 189 183 183 169 D RIGHT 29 699 699 699 670 A MAJOR STREET WB LEFT 21 424 424 424 403 A IDENTIFYING INFORMATION NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE AN' -IS am noon Pm OTHER INFORMATION_... 992 with dev sensitivity CAPACITY AND LEVEL -OF -SERVICE Page-3 1985 HCM: UNSIGNALIZED INTERSECTIONS paQe_1 --'-CITY----LEVEL-------------------'--- -----------------___----- H.M.t YZY Y.i�ttXlt:4FYYYYYIKXXtt 1.%2Yt�Y'.KtYKX.CXYKY>.M Y��IK'M'.Y.hX<t�YXYX�'K�tYt'.K IK't ' POTEN- ACTUAL IDENTIFYING INFORMATION ' FLOW- TIAL MOVEMENT SHARED RESERVE -------------------------------------------------------------------- RATE CAPACITY CAPACITY CAPACITY CAPACITY i MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS AVERAGE RUNNING SPEED, MAJOR STREET.. 30 p M ------------ SH R SH ------------ --- PEAK HOUR FACTOR ..................... ' .93 ------- -------- --------- MINOR STREET see - AREA POPULATION ...................... 100000 i NB LEFT 83 163 131 131 49 E NAME OF THE EAST/WEST STREET......... west elizabeth RIGHT 138 813 813 813 675 A NAME OF THE NORTH/SOUTH STREET....... access MAJOR STREET NAME OF THE ANALYST .................. mid WB LEFT 155 589 589 589 434 A DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am noon pm IDENTIFYING INFORMATION OTHER INFORMATION.... 1992 with dev sensitivity --- --------- ------------------------ --------- --------------- ------ NAME OF THE EAST/WEST STREET...... west elizabeth INTERSECTION TYPE AND CONTROL NAME OF THE NORTH/SOUTH STREET.... access --------------------------------------------------------------------- DATE AND TIME OF THE AN3 /92 am noon Pm OTHER INFORMATION.... 1992 with dev sensitiviL INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- EB WB NB SB ---- ---- ---- --- LEFT 0 131 70 -- THRU 438 423 0 -- RIGHT 77 0 117 -- NUMBER OF LANES E8• WB NB SR ------- _______ _______ _______ LANES 2 -- 1985 HCM: UNSIGNALIZED INTERSECTIONS Pape-1 IDENTIFYING INFORMATION --------------------------------------------------------------------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .93 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am noon Pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- EB WB NB SB ---- ---- ---- ---- LEFT 0 71 47 -- THRU 465 604 0 -- RIGHT 54 0 46 -- NUMBER OF LANES --------------------------------------------------------------------- EB WE. NB SB --------------------- LANES 2 2 ------- I CAPACITY AND LEVEL -OF -SERVICE Page-3 POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (PCPh) c (pcph) c = c - v LOS P M SH R SH MINOR STREET 1J-Z'1 Sec NS LEFT 56 130 118 118 62 E -RIGHT 54 811 811 811 757 A MAJOR STREET WB LEFT 84 585 585 585 501 A IDENTIFYING INFORMATION -------------------------------------------------------------- NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS/3am noon Pm OTHER INFORMATION.._. sensitivity 1992 with de sensitivity APPENDIX E 1985 HCM: UNSIGNALIZEU INTERSECTIONS Page-1 IDENTIFYING INFORMATION ---------------------------------------------------------------- AVERAGE RUNNING SPEED. MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .74 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. noon pm 8 OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES ----------------------------------------------------------------- EE WB NB SB. ---- ---- ---- ---- LEFT 0 13 9 -- THRU 595 146 0 -- RIGHT 13 0 16 -- NUMBER OF LANES ------- ------------------------------------------------------------- EB WE; N6 SE; ------- ------- ------- LANES 2 2 2 ------- -- CAPACITY AND LEVEL -OF -SERVICE Page-S POTEN- ACTUAL FLOW- TIAL MOVEMENT SHAPED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH ------ ----------------- ------------------------ --- � gev MINOR STREET (y"I NB LEFT 13 183 178 178 165 D i RIGHT 27 692 692 692 665 A MAJOR STREET WB LEFT 19 415 415 415 395 B IDENTIFYING INFORMATION ------------------------------------------------------- NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS..... 2/3 92 : am noon pm OTHER INFORMATION.... 1992 with dev sense ity i 1985 HCM: UNSIGNALIZED INTERSECTIONS Page-1 IDENTIFYING INFORMATION AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR FACTOR ..................... .98 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED.. ........ ...... am noon pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL --------------------------------------------------------------------- INTERSECTION TYPE: T-INTERSECTION MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES --------------------------------------------------------------------- EB WB NB SB ---- ---- ---- ---- LEFT 0 131 70 -- THRU 482 465 0 -- RIGHT 77 0 117 -- NUMBER OF LANES -------------- EB WB NB SB, ------- ------- ------- ------- LANES 2 2 2 -- CAPACITY AND LEVEL -OF -SERVICE Page-3 -------------- --------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH ------------------------------------------------ --- MINOR STREET 19-Zq Sec NB LEFT 79 155 126 126 48 E RIGHT 131 805 805 805 673 A MAJOR STREET WB LEFT 147 576 576 576 429 A IDENTIFYING INFORMATION ------------------------------------------------------ NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS..... 2/3/92 : am noo Pm OTHER INFORMATION.... 1992 with dev sensitivi y 1985 HCM: UNSIGNALIZED INTERSECTIONS Page-1 f iXXtIKY'A'i Y]K�Y. t'K.'K�tYY Y.i�>.YX'M W.t�Y.Y YY�Y�KXYYW. t Ik>.lC>Y YtC�>. t lK#t'N.MYZ�Z>.t Y.Y ttX IDENTIFYING INFORMATION ------------------------------------------------------------------- AVERAGE RUNNING SPEED, MAJOR STREET.. 30 PEAK HOUR'FACTOR..................... .98 AREA POPULATION ...................... 100000 NAME OF THE EAST/WEST STREET......... west elizabeth NAME OF THE NORTH/SOUTH STREET....... access NAME OF THE ANALYST .................. mid DATE OF THE ANALYSIS (mm/dd/yy)...... 2/3/92 TIME PERIOD ANALYZED ................. am noon pm OTHER INFORMATION.... 1992 with dev sensitivity INTERSECTION TYPE AND CONTROL -------- ------------------------------------------------------------ INTERSECTION TYPE: T-INTERSECTIONS MAJOR STREET DIRECTION: EAST/WEST CONTROL TYPE NORTHBOUND: STOP SIGN TRAFFIC VOLUMES ------------------------------------------------------------------ EB WB NB SB ---- ---- ---- ---- LEFT 0 71 47 -- THRU 511 664 0 -- RIGHT 54 0 46 -- NUMBER OF LANES -----------------------------------------------------------------' EB WB NB SB --------------------- LANES 2 2 2 ------- -- CAPACITY AND LEVEL -OF -SERVICE Page-3 --------------------------------------------------------------------- POTEN- ACTUAL FLOW- TIAL MOVEMENT SHARED RESERVE RATE CAPACITY CAPACITY CAPACITY CAPACITY MOVEMENT v(pcph) c (pcph) c (pcph) c (pcph) c = c - v LOS p M SH R SH ------- -------- --------- ----------- ------------ --- MINOR STREET 1j' t1 sew NB LEFT 53 123 ill 711 59 E RIGHT 52 802 802 802 750 A MAJOR STREET WB LEFT 80 572 572 572 492 A IDENTIFYING INFORMATION ------------------------------------------------------- NAME OF THE EAST/WEST STREET...... west elizabeth NAME OF THE NORTH/SOUTH STREET.... access DATE AND TIME OF THE ANALYSIS..... 2/3/92 ; am noon pm OTHER INFORMATION.... 1992 with dev sensitivity blocked. However, there is a second access to the Diamond Shamrock located approximately 160 feet south of West Elizabeth. The prudent driver will proceed to this access if problems arise closer to West Elizabeth. While the entrance driveway to Taco Bell is located very close to West Elizabeth Street, no operational problems were observed at this location. The exit from the Taco Bell drive -through is located approximately 90 feet south of West Elizabeth Street. During traffic counting, the exits from the access driveway to West Elizabeth never extended this far and, therefore, there were no operational problems observed at this exit. The additional traffic generated by the Potts PUD should not cause problems at the exit from the Taco Bell drive -through. It is concluded that the peak hour operation with the additional Potts PUD traffic will be acceptable. It is recommended that pavement markings be placed on the access driveway and suitably maintained. I WEST ELIZABETH. STREET 541 /438/465 13/76/54 Q Taco Bell w 0 -*-133/423/604 .� 1 1 / 126/65 SITE Diamond Shamroc AM / Noon / PM. 1992 PEAK HOUR TRAFFIC Figure 1 Table 1 Existing (1992) Peak Hour Operation Level of Service 1985 Highway Capacity.Manual Intersection AM NOON PM W. Elizabeth/Access Driveway NB LT D (A/B/C)* E (C/D)* E (C/D)* NB RT A A A WB RT A A A * Operation considering the recent research and expected delay Table 2 Trip Generation A.M. Peak Noon Peak P.M. Peak Land Use Trips Trips Trips Trips Trips Trips in out in out in out Potts PUD - 26 D.U. Non -school 1 3 2 2 3 2 vehicle trips School person 1 14 8 2 8 2 trips School vehicle 1 7 4 1 4 1 trips Total vehicle trips 2 10 6 3 7 3 W 25% / Nom. 75% / 100% SITE Non -School / School Q N TRIP DISTRIBUTION Figure 2 D Q N �--133/423/604 WEST ELIZABETH STREET ,0(-13/131/71 541 /438/465 —► 13/77/54 � Q Taco Bell W oc c N N W U V Q SITE EXISTING PLUS POTTS P.U.D. PEAK HOUR TRAFFIC qDiamond §9c AM / Noon / .PM Figure 3 -0146/465/664 WEST ELIZABETH STREET /-13/131/71. 595/482/511 13/77/54 Taco Bell EXISTING x 10% PLUS PEAK HOUR TRAFFIC SITE Diamond hamroc AM / Noon / PM POTTS P.U.D. Q N Figure 4