Loading...
HomeMy WebLinkAboutAGENDA REPORT 1997 0115 CC REG ITEM 10OAGENDA REPORT C = TY OF MOORPARK TO: The Honorable City Council (A-- FROM: Kenneth C. Gilbert, Director of Public Works DATE: January 3, 1997 (Council Meeting 1- 15 -97) SUBJECT: Consider Traffic Signal and Intersection Design at Moorpark Road and Tierra Rejada Road BACKGROUND 1. In April 1996 the City completed a project for the installation of a traffic signal at the subject intersection. The design for that traffic signal provides for a permissive /restrictive left turn phase for west -to- south left turners. As you may know, such a design provides for a restricted left turn phase (left green arrow) , followed by permissive left turns on a GREEN light (green ball) as gaps in the traffic allow. 2. In October 1996 the City Council directed the City Traffic Engineer to perform a traffic study at this intersection for the purpose of identifying any desirable safety improvements. One possible outcome of that study would be the elimination of the permissive /restrictive left turn phase, with left turns restricted to a GREEN ARROW only. DISCUSSION Attached as Exhibit 'A' is a copy of the Traffic Engineer's Report on this matter. A summary of that report is as follows: 1. Speed: The report does not include any recent speed survey information. The Speed Surveys being prepared by another consultant (including a Speed Survey for this segment) have not yet been completed. It was the opinion of the engineer that this information was not required to complete this analysis. apktr3 000278 8 Traffic Signal Moorpark Road / Tierra Rejada Road January 1997 Page 2 2. Accidents: There have been eleven (11) accidents during 1996, an increase over prior years. Many of those accidents involve west -to -south left turn traffic. A summary of the possible causes for this increase in the accident rate is set forth on page 3 of the report. 3. Alternative Solutions: A number of solutions are listed on page 6 of the report. Those alternatives include the following: A. Remove the permissive /restrictive left turn phase. B. Prohibit left turns. C. Construct double left turn lanes for west -to -south traffic. D. Extend the median for the east leg westerly. 4. Recommended Alternative: The recommended alternative solution is Alternate D: modify the intersection by extending the raised median for the east leg westerly approximately sixty feet (601) to the west. This would result in moving the STOP bar to the west and installing additional traffic loop detectors. The net effect of this change would be that staged left turn traffic would have a shorter distance to travel through the intersection. The amount of time required for this turning movements would, therefore, be reduced. This would allow vehicles to make this turn during the permissive phase (GREEN BALL) in a shorter period of time. It is believed that this change will be a considerable improvement over existing conditions which tend to place traffic in the path of on- coming traffic, for a longer period of time. 5. Fiscal Impact: If modifications to the traffic signal are directed, it is the intent of staff to request an additional appropriation and budget amendment at a later date when all costs are known. It is recommended that the City Council direct staff to proceed with a project for the modification of the intersection as described in Alternate 'D' in this report. mpktr3 OW25U DRAFT 92120196 STUDY OF FACTORS AFFECTING SAFETY AT THE INTERSECTION OF TIERRA REJADA ROAD AND MOORPARK ROAD INTRODUCTION The City of Moorpark has been concerned about conditions at the intersection of Moorpark Road and Tierra Rejada Road for several years_ The City conducted a traffic warrant study of the intersection in mid -1995 and found that a traffic signal was warranted. Based on that study, the City proceeded with the design and construction of a traffic signal, which was activated earlier this year. Traffic accidents have increased over the past six months. The City now wishes to study the intersection to determine if there are actions which can be taken to make the intersection safer. EXISTING CONDITIONS The intersection of Tierra Rejada Road and Moorpark Road is a 3 -way intersection laid out on a skew of approximately 75 degrees. Tierra Rejada Road is an arterial street with two 12 foot through lanes in each direction of travel, a paved 8 foot outside shoulder and a 14 foot wide raised median. At the intersection there is a striped east bound right turn lane. A west bound left turn lane is protected by the raised median. The left turn lane is 220 feet long including taper. Moorpark Road is a rural collector street with one 12 foot travel lane in each direction and narrow paved shoulders. At the intersection, the pavement is flared and there is a left turn lane, as well as a right turn merge area which is striped. An ongoing study by Ventura County may result in realigning Moorpark Road within a 2 to 5 year period. The intersection is located in an area surrounded by farmland with no development within 1,000 feet of the intersection. Sight distance is good for each of the three approaches. The signal design engineer determined that the sight distance for the left turn movement to the south is 850 feet, which meets the CalTrans standard. Formal speed studies have not been conducted. However, from observations by both City police officers and the Traffic Engineer, vehicles frequently exceed the posted 45 mph speed limit. However, excessive speed (more than 60 mph) does not appear to be a major problem. Total accidents at the intersection by year are as follows: 1993 4 1994 7 1995 7 1996 11 (through 12/19) mft%0281a2 000281 SE NI P'e'r , .,t'ah 111- 7 V_. " — DRAFT 92120196 Seven of the 11 accidents for 1996 involve left turning vehicles from Tierra Rejada Road to south bound Moorpark Road. Based on these accident statistics, it is desirable to take actions to reduce the left turn accidents. Peak Hour traffic volumes are shown in Figure 1 The Level of Service (LOS) for the intersection, ) assuming 31.4% of left turns are on the permissive phase, is g in the AM peak hour and b in the PM peak hour. The LOS calculations are shown in Table 1. Four sets of observations and sample traffic counts in both the morning (7:00 - 8.00am) and the evening (6:00- 7:00pm) peak hours of operations were conducted during the period of November 20, 1996 through December 11, 1996. Significant observations made during that period are as follows: • AM peak left turn volumes onto Moorpark Road stack up on Tierra Rejada Road from Moorpark Road to the SR23 south bound ramps, blocking one through lane of traffic on Tierra Rajada Road. Turning vehicles require more than one cycle of green to dear the intersection. • A majority of the AM peak turning vehicles are using Moorpark Road to avoid congestion on SR23 south bound. PM peak left turn volumes onto Moorpark Road are only about 75% of AM peak volumes. These are still considerable delays for the PM peaks. • 70% of sampled AM and PM peak left turns are made under the green ball (permissive turns). • 5% of the sampled AM and PM peak left turns are made when the west bound movement has a red ball and the turn arrow is not on. 2 mi30028142 Ml SENT BY DA] GHT PREW4 & .�����! „ �.� _;, DRAFT 12/20196 FACTORS WHICH CONTRIBUTE TO ACCIDENTS Afta -r careful review of the physical characteristics and traffic flows at the intersection, there are several factors which appear to contribute to the accidents occurring at the intersection of Moorpark Road and Tierra Rejada Road. These factors are as follows- Left turning vehicles are stopped by a stop bar which is positioned 88 feet east of the centerline at Moorpark Road. projected onto Tierra Rejada Road. This positioning may cause a delay in a left turning vehicle making the turn and clearing the east bound travel lanes on Tierra Rejada. When the time for the left turning vehicle is calculated, the total separation from an east bound vehicle is excessive (45 mph = 716 feet, 60 mph = 926 feet). The calculations are shown on Attachment 1. South bound SR 23 traffic is using Moorpark Road as a "cut off" route to reach North bound SR 101. The volume of this traffic in the morning peak hour is approximately 538 vehicles and, by observation, approximately 95 percent of the vehicles make a left turn onto Moorpark Road. The AM peak hour volume of left turning vehicles is 730 vehicles/hour. At this volume, 12 vehicles per minute are making the turn. Currently, only about 5 vehicles per green cycle are able to make the turn. For a period of approximately 30 minutes in the AM peak, the queue for the left turn stretches from the intersection to approximately the SR 23 ramp. • The intersection is isolated and with the peak hour congestion and delays, drivers do not observe traffic laws and traffic control devices. Four "near misses" (where vehicles had to apply maximum braking and/or change direction) were observed during the four days of observation. 41 misbD28142 000223 SEV . JAA Y- - IAN - - �i : _ . . 11 1 - TABLE 'I DRAFT 12120196 TIERRA RAJADA ROAD - MOORPARK ROAD LEVEL OF SERVICE CALCULATIONS WITH PERMISSIVE LEFT TURNS Movement Capacity AM Volume PM Volume VIC AM V/C PM SBR 0 0 0 0 0 SBT 0 0 0 0 0 SBR 0 0 0 0 0 WBR 0 0 0 0 0 WBT 3,200 351 1,215 .11 .38+ WBL ' 1,600 229 173 .14' .10* NBR 1,600 465 343 .29 .21 NBT 0 0 0 0 0 NBL 1,600 fit 386 .04' .24" EBL 0 0 0 0 0 EBT 3,200 1,241 496 .39 .16 EBR 1,6001 240 142 .15 .09 TOTAL YELLOW LOS .57* .72 .10 .10 .6716 .82 /D '31,4% OF ALL TURNING VEHICLES TURN ON GREEN ARROW CYCLE 4 m1=0281-92 000284 SENT 13 I'j) (J" _11.1_ir_- Lq t I1_,_. ATTACHMENT 1 DRAFT t V20/96 Calculation of t,,,, which is total time for a west bound vehicle to turn left and clear the intersection. ta, = t ,+ t , + t2 Where: 4 is driver's reaction time -- assume .75 seconds. t, is the time to drive from stop bar to center line projected of Moorpark Road. t2 is the time to drive from centerline south across the east bound lanes and clear the intersection. ASSUME: Acceleration = 3.3 mph /sec (0 mph to 60 mph in 18 seconds) distance from stop bar to centerline of Moorpark Road. t, = 12d /A = 1176 feet/ 4.9 f /s/s = 5.99 sec to reach centerline from stop bar t2 = 2dN Where: d = (12 feet + 12 feet + 16 feet) = 40 feet v = txA = 5.99 sec x 4.9f /s/s = 29.4 feet /sec t2 = 2(40)feett 29.4feet/sec = 2.7 sec =G +t, +t2 =.75 +5.99 +2.7 = 9.5 sec Distance EB traffic travels in t,,,,, Assume 45 mph Assume 60 mph d =t, xV d =t,xV = 9.5sec x 45 mph x 1.47m /m/ s/h = 9.5sec x 60 x 1.47 = 837.9 feet = 628.4 feet Total required separation between East bound vehicle and left turning east bound vehicle at beginning of left turn movement: 45 mph = 628.4 + 88 = 716 feet 60 mph = 837.9 + 88 = 926 feet 5 mix1028i42 lut)0285 SENT BY :DWIGHT FRENCH & ASx N IF t _ DRAFT 12120/96 ALTERNATE SOLUTIONS Several approaches were considered to solve the left turn related traffic accident problem. These alternates are: A. Remove the permissive phase for left turn vehicles. This would result in very severe congestion in the intersection -- AM peak hour would result in an LOS of E and PM peak hour would result in an LOS of F. Table 2 shows the LOS calculations. This approach should only be used as a last resort. B. Restrict left turns to Moorpark Road. This action would solve the accident problem. Signs would need to be posted on SR 23 south bound, as well as on Moorpark Road. This action would need City Council support. Prohibition would be opposed by significant numbers of drivers. C. Construct dual left turn lanes on Tierra Rejada Road and widen Moorpark Road for a distance of a least 750 feet south to the 2 south bound lanes. This approach would be most expensive at $134,800 for design and construction. Approximately $75,000 would have to be spent in Ventura County. Also, this intersection is likely to be modified in the near future. D. Move the median end at the west end of the left turn lane on Tierra Rejada Road, approximately 60 feet westerly and place the stop bar for the left turn at the new median end. Signal detector loops would also have to be repositioned. This will reduce the time for a left turn vehicle to dear the intersection by 2.6 seconds and reduce the separation needed at 45 mph to 484 feet and at 60 mph to 637 feet which is well within the existing sight distance. The cost of this approach is approximately $9,700. E. Provide additional law enforcement activity at the location. This is a need based on the observed 5% of left turns on red and speeds on Tierra Rejada Road. This would be necessary in conjunction with Alternates A, B and D. N miscW28142 ()00z86 _ II SE'A'T BY Y 1 Gl -1 "! - - �r - „� , _ - - _ • - - � _ � .. ,, DRAFT 12/20096 TABLE 2 TIERRA REJADA ROAD - MOORPARK ROAD LEVEL OF SERVICE CALCULATIONS WITHOUT PERMISSIVE LEFT TURNS Movement Capacity AM Volume PM Volume V/C AM V/C PM SBR 0 0 0 0 0 SBT 0 0 0 0 0 SBR 0 0 0 0 0 WBR 0 0 0 0 0 WBT 3,200 T 351 1,215 .11 .38" WBL 1,600 730 550 .46" .34' NBR 1,600 465 343 .29 .21 NBT 0 0 0 0 0 NBL 1,600 62 386 .04" 24 EBL 0 0 0 0 0 EBT 3,200 1,241 496 .39 _16 EBR 1,600 240 142 .15 .09 TOTAL YELLOW LOS .89" .96 .10 .10 .991E 1.061F 7 miac=8142 ()VV ?S SENT 31 : ) G- .... : � .. _ DRAFT 12/20/96 RECOMMENDATIONS It is recommended that alternate D, move the Terra Rejada median westward by 60 feet be implemented in conjunction with Alternate E, increased law enforcement. It is further recommended that the City of Moorpark continue to monitor accidents and operation of the intersection, after an of the recommendations of this report are implemented. If a high rate of left turn related accidents continue, additional alternates should be considered. E�3 miSM028142 0(0288