The Traffic At the New High School: an Evaluation

Professor Donald Meyer , October 11, 2004

The major unresolved problem at the proposed new high school on Maple Road is how to handle traffic at the start and end of the school day as well as at large events. Our understanding is that a complete traffic study is being prepared. It is essential. However, it is easy and more transparent to make a simple calculation. At the beginning and end of the school day approximately 1000 carsnote (students, staff, drop-offs and local non-school traffic) must pass under M-14 just south of the school in 30 minutes, north in the morning and south after school. Stoplights will certainly have to be installed north and south of M-14 at the exit and entrance ramps. Because of the many possible traffic movements at M-14 these lights will be green for Maple Road traffic no more than 30% of the time in each cycle.

With the above input a simple calculation is possible. When a row of cars stopped at a stoplight begins moving, cars follow each other at intervals of about 2 seconds, a flow rate of 30 cars/minute for each lane when the light is green. The flow rate when the stoplight is taken into account will be 30 x 0.30 = 9 cars/minute. If there were only school traffic it would take 700/9 = 78 minutes to get the traffic under M-14 where 700 is the total school traffic as detailed at the bottom of the pagenote. When there are in addition 3 cars/minute of local traffic it will take 700/6 = 116 minutes, almost 2 hours, to get all the students to school! This is clearly unacceptable. In addition, all-school events such as music sports, drama, etc. where parents might be involved would be almost impossible to hold.

Only drastic action, such as requiring all students to come on buses, would create even a marginally acceptable traffic situation and does not help with all-school activities. Enforcing such a provision would inevitably cause parking to migrate to streets in surrounding areas (Oak Hills, Blueberry, Craig, etc. plus Garden Homes and Walnut Ridge). This is what worries people in the neighborhoods around the school.

Why is it so difficult to get students to the school? The way this location differs from that of a desirable location is that the bulk of the traffic comes from one direction and must cross a major freeway interchange. That adds a factor of 2 for direction and 3 for stoplights, or a factor of 6, to the time to move cars.

Note: Local non-M-14 traffic: 3 cars/minute; Staff: 200 cars; Student drivers: 500 cars. Of the 1600 students it is assumed that 10% come from north of the school. The rest are divided equally between student drivers drop offs and buses, 480 each. We assume that the 960 student drivers and drop offs have an average of two students per car, thus, 480 cars that we round to 500 to include buses.