Wednesday, April 21, 2010

Series of 4-way stops - Dean Rd between Beacon St and Chestnut Hill Ave., Brookline

Created by Justin Phuc Huynh

Dean road is a two-way street located between Chestnut Hill Avenue and Beacon Street in Brookline, Massachusetts. According to the map, Dean Road could be used as a short cut for motorists who want to get from Chestnut Hill Avenue going East to Beacon St or those who from Beacon St want to go South through Chestnut Hill Avenue. However, the main purpose of this road is to serve a residential area, a school, and a playground. Town of Brookline uses series of four-way stops at any four-way intersection along Dean road in order to acheive the following treatments:

  • Bring motor vehicles to full and complete stop (able to keep vehicles at slow speed around 250 feet after each stop)
  • Maitain motor vehicles at low speed (20 -30 mph) along the whole road.
    =>Provide good service for the neighborhood by making it safer for pedestrians.
Unfortunately, the distance between two four-way intersections on Dean Road is approximately 600 feet apart. Having only four-way stop signs is not possible to maintain the vehicle at low speed along the whole road. In order to overcome this issue, Town of Brookline makes a use out of multiple traffic calming signals and signs:

At the intersection between Fisher Avenue and Dean Road, besides using stop sign, there is also a flashing red lights are set up in the middle of the intersection. Flashing red lights serve the same purpose as the four-way stop signs do. However, the lights are installed high up in the middle of the intersection that makes it easier for motorists to see and be caution from further away.
Yellow sign with red polygon and up arrow is used to alert motorists that there is a stop sign ahead. This sign helps to reduce the vehicle speed.
At three-way intersections along Dean Road, It is effective enough to use Pedestrian signs instead of four-way stop signs. The Peds signs are used to force motorists to yield and be caution of crossing pedestrian. According to the map, three-way intersections are located less then 250 feet from four-way intersections (stop signs) meaning the motorists most likely to travel at low speed before they meet the pedestrian signs.

“School zone ahead” sign is used to force motorists to slow down and be caution of a school's area ahead.
An electronic speed limit sign with flashing yellow light is used to force motorists to slow down to at most 20 mph because there is a school ahead.

Yellow sign with two walking pedestrians and their book bags is located about 20 feet after the electronic speed limit sign (picture above) also used to force motorists to slow down and caution of students crossing the road.

A yellow sign with two kids playing on the seesaw also forces motorists to slow down and be aware of a playground ahead.


Putting a pedestrian sign in the middle of the road also forces motorists to slow down and be caution of pedestrians crossing the road
Allowing parking along the road makes the one lane road become narrower. This is one way of making travelling vehicles to slow down or maintain their current low speed.

Overall, the design successfully achieves its goal of making the road a safe environment for the residential area, school, and playground. However, the aspect of using four-way stop signs alone does not fulfill the purpose completely. Combining other aspects of traffic calming treatments as shown above makes a success. Furthermore, the design could be more effective by adding some improvements such as:
  • Putting two speed humps between the three four-way intersections. This would make the road extremely effective because motorists most like not able to pick up a high speed after stopping at stop sign and approaching a speedhump about 250 - 300 feet ahead.
  • Using more flashing red lights. This is to be conservative for motorists.
  • Putting medium refuges at the wide four-way intersection (Dean Road vs. Druce Street, photo below). This makes it easier and safer for pedestrians to cross the road.

1 comment:

  1. Not sure what is meant by 3-way intersections; do you mean at Beaconsfield?
    Stop signs are a stronger point treatment than speed humps. While speed humps slow a car to 12-15 mph, stop signs slow them to 0-2 mph. With a stronger point treatment, a larger spacing can be effective. The big question about this site is whether stop signs with this larger spacing is effective at keeping cars from going fast between the stop signs; unfortunately, I don't see a clear answer. Many of the other signs mentioned are normally considered ineffective, routinely ignored by motorists; if there is any speed control, at least 98% of it comes from the stop signs.

    Good idea for a median refuge. However, because there's a stop sign, it's already a low stress, high safety crossing, so I'd put my median refuge money somewhere else. But it's good to keep in mind if the street is rebuilt.