Traffic Study-Pecos

ALMA SCHOOL ROAD AND PECOS AVENUE

TRAFFIC ENGINEERING STUDIES NOVEMBER 16, 2000

CITY OF MESA TRANSPORTATION

MESA, ARIZONA



INTRODUCTION

At the request of Ms. Roberta Laidman of 1160 W. Obispo Avenue and Mr. Ron Mellinger of 1152 W. Obispo Avenue, a traffic signal warrant study was conducted for the intersection of Alma School Road and Pecos Avenue. Ms. Laidman and Mr. Mellinger are concerned about safety and delay at the intersection.
A location map is attached. See Figure 1.

PHYSICAL AND TRAFFIC CHARACTERISTICS

Alma School Road is a fully improved major arterial street consisting of two northbound lanes, two southbound lanes, and a continuous left turn lane. Alma School Road carries approximately 45,900 vehicles per day and has a posted speed limit of 45 mph. Street lighting is provided, and parking is prohibited.

Pecos Avenue is a fully developed 44 foot wide street which serves as a collector street for the neighborhoods east and west of Alma School Road. On-street parking is permitted, and street lighting is provided. Pecos Avenue carries approximately 860 vehicles per day on its eastbound approach and 1,000 vehicles per day on its westbound approach to Alma School Road. Pecos Avenue east of Alma School Road has an unposted speed limit of 25 mph and speed humps. Pecos Avenue west of Alma School Road has a posted speed limit of 25 mph. No striping is provided on Pecos Road at its intersection with Alma School Road.

Land use in the area is single family residential. No homes face onto Alma School Road. Existing traffic control consists of stop signs for eastbound and westbound traffic on Pecos Avenue at Alma School Road.

ANALYSIS

Traffic counts were taken on October 10, 11, and 12, 2000. The October 12, 2000 counts were used for this evaluation because this day had the highest number of vehicles approaching the intersection of the three days the intersection was counted. Of the eleven signal warrants that are evaluated for a traffic signal study, only the peak hour volume warrant was satisfied for traffic volumes. Copies of counts and summaries of traffic signal warrants are attached. See Appendix A.


Delay observations were conducted on November 2, 2000 from 7:00 am to 8:00 am and from 5:00 pm to 6:00 pm. These time frames were chosen because traffic count data indicated them to be the peak traffic times. Observations were also conducted between 2:50 pm and 3:30 pm. The 7:00 am to 8:00 am time frame and 2:50 pm to 3:30 pm time frame coincide with Dobson High School arrival and release times, respectively. There is a rear entrance to the high school located on Saguaro Circle west of Alma School Road.

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During the 7:00 am to 8:00 am observations there were 88 eastbound vehicles and 86 westbound vehicles that approached the intersection. Of the 88 eastbound vehicles, 78 (or 88.6%) turned right, 10 (or 11.4%) turned left. Of the 86 westbound vehicles, 77 (or 89.5%) turned right, one went straight through, and eight (or 9.3%) turned left. There were 19 pedestrians observed crossing Alma School Road in the area of the intersection. Adequate gaps in traffic were present to accommodate the pedestrian crossings.

Average delay for all drivers on Pecos Avenue approaching Alma School Road during this observation was approximately 12.5 seconds per vehicle. Delays up to two minutes were observed for left turning drivers on Pecos Avenue, with the average delay for left turning drivers being approximately 59 seconds. This delay is to be expected for drivers on a minor collector street approaching a major arterial street during the peak traffic times. Drivers on Pecos Avenue making right turns, the movement made by 89% of the approaching traffic, experienced little delay.

The 2:50 pm to 3:30 pm observation for pedestrians coincides with the release of Dobson High School. During this time frame, there were 13 pedestrians observed crossing Alma School Road at or near intersection. Adequate gaps in traffic were present for the majority of these crossings. Typically, these crossings were made in a conscientious manner. Pedestrians crossed half of the street at a time as lanes cleared and gaps in traffic became present.

During the 4:00 pm to 5:00 pm observations there were 86 eastbound vehicles and 53 westbound vehicles that approached the intersection. Of the 86 eastbound vehicles, 71 (or 82.6%) turned right, two went straight through, and 13 (or 15.1%) turned left. Of the 53 westbound vehicle, 42 (or 79.2%) turned right, two went straight through, and nine (or 17.0%) turned left. There were two pedestrians observed crossing Alma School Road in the area of the intersection. Both of these crossings were made in a conscientious manner with each pedestrian crossing a half street at a time when gaps in traffic were present.

Average delay for all drivers on Pecos Avenue approaching Alma School Road during this observation was approximately 18.3 seconds per vehicle. Delays exceeding one minute were observed for left turning drivers on Pecos Avenue, with the average delay for left turning drivers being approximately 29 seconds. Although left turning drivers on Pecos Avenue experienced more delay than the right turning drivers, the overall average delay is less than what would be experienced if a traffic signal were to be installed. Adequate gaps in traffic were available for right turns, left turns, and through movements.

Only the peak hour volume warrant was satisfied for traffic volume. However, this warrant is intended for application when traffic conditions are such that the minor street suffers undue delay in entering or crossing the major street. Field observations indicate that the overall delay experienced by drivers on Pecos Avenue approaching Alma School Road is less than what would be experienced if a traffic signal were to be installed on the basis of this warrant alone.

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A review of accident frequency history revealed three reported intersection related accidents between January 1, 1998 and December 31, 1998. Of these three accidents, none were of the right-angle type. A right-angle type accident is the type of accident that is considered potentially preventable by the installation of a traffic signal.

Between January 1, 1999 and December 31, 1999 there were five reported intersection related accidents. Of these five accidents, three were of the right-angle type.

Between January 1, 2000 and October 3, 2000 there have been two reported intersection related accidents. Neither of these accidents was of the right-angle type. Collision diagrams are attached. See Figures 2, 3, and 4.

RECOMMENDATION

Because none of the eleven signal warrants is considered to be satisfied and there is a low right-angle accident frequency, it is recommended that a traffic signal not be installed at the intersection of Alma School Road and Pecos Avenue. Although some delay exists for left turning drivers during the peak hours, little overall delay exists for the major traffic movement from Pecos Avenue, right turns. Installation of a traffic signal would likely increase the overall delay for drivers on Pecos Avenue and would cause undue delay for drivers on Alma School Road.

Average delay for all drivers on Pecos Avenue approaching Alma School Road during this observation was approximately 13.5 seconds per vehicle. Delays up to two minutes were observed for left turning drivers on Pecos Avenue, with the average delay for left turning drivers being approximately 33 seconds. This delay is to be expected for drivers on a minor collector street approaching a major arterial street during the peak traffic times. Drivers on Pecos Avenue making right turns, the movement made by 89% of the approaching traffic, experienced little delay.


Report by: Dale Brunk, Jr., Senior Traffic Studies Analyst