Ralston Traffic Impact Due to CSUS Project

[Editor's Note: The following is a blog post from Patch user, Suresh Yegnashankaran regarding the proposal by Crystal Springs Uplands School to construct a new middle school on Davis Drive in Belmont. Anyone wishing to blog for Belmont Patch on this, or other topics, may do so by clicking here.]

In an email to Mr Eric Reed of Belmont Planning Commission, I had submitted the following as my supporting analysis for estimating additional traffic delays on Ralston, if the (Crystal Springs Uplands School) CSUS project is implemented.

The analysis focuses on expected AM traffic delays on Ralston Ave during commute hours of 7:30 am to 8:30 am.

For those Belmont residents who have to get to 101 or 280 via Ralston Ave., crossing a few intersections, between 7:30am and 8:30 am - I believe their morning commute delays can be expected to increase by about 10 to 20 minutes, 15 minutes on average over many days depending on where one lives.

This estimate is a "median" or "mode", meaning commonly experienced total delay on Ralston Ave. in the mornings. On a random basis, different drivers will face such delays on different days, facing better or worse delays on other days.

Details:

The estimate is based on about 100 to 140 additional vehicles on Ralston during a 15 minute window of CSUS drop-off time.  These are based on effective implementation of TDM efforts - 210 students, one-third to use car pooling and another third to use bus-van pooling. Not knowing specifics, it is fair to assume half of these vehicles will be in each direction of Ralston. Depending on where a Belmont resident lives, there will be 4 to 8 intersections to cross for those who have to go thru Ralston traffic to get to 280 or 101.

These numbers will result in an additional arrival rate of about 4 vehicles per minute at each of the Ralston intersections, during the 15 minute window. According to the initial CSUS project study draft, during the current RMS school drop off period of 8:00 am to 8:15 am, an average service rate (LOS) of about 3 vehicles per minute is estimated. This will result in an additional queue accumulation of 1 vehicle per minute at each intersection of Ralston;  which in turn will result in an average additional delay of 2.5 minutes per vehicle per intersection.

(An additional queue accumulation of 15 vehicles in 15 minutes; a service time of 3 vehicle per minute; resulting in an additional delay of 0 to 5 minutes, at random, for each driver at each intersection.  This will average,  over many days,  to 2.5 minutes per driver per intersection; which is 10 to 20 minutes per driver depending on where one lives. For simplicity, a statistically "uniform distribution" has been assumed for arrival and service rates.  In reality these rates follow a poisson distribution, under which the queue lengths and delays will be even worse.)

Mitigation assumptions:

1. Results of planned TDM efforts are taken into account in the above estimate.

2. Staggered timings with RMS:  CSUS starting-ending times are planned to be staggered with respect to RMS.  If so, the peak drop off window for CSUS will be 7:30 am to 7:45 am.     

The above staggering will undoubtedly avoid a dramatic increase in delays for the same group of people, those who will be driving on Ralston around 8:00 am to 8:15 am, the RMS drop-off window.  On the other hand, a new group of people driving on Ralston between 7:30am and 7:45 am will face an additional average delay of 15 minutes as detailed above.  For this new group of drivers, compared to the RMS window group of drivers, the 15 minute window will be significantly more toward the routine AM peak-hour traffic.

Based on the above analysis, it wiil be worth considering CSUS starting time to be 8:30 am, instead of 7:45 am.   

Suresh