Tuesday, April 24, 2012

Traffic Calming without using Physical Measures

by Nathan Gottier

Traffic Calming is the broad title for a practice of street design. The goal of these designs is to "Prevent motorized traffic from killing other street functions by virtue of speed". There are two main ways to calm the streets and make them safer. The first is volume control. For this, I observed the neighborhood Eastman, Elder, and Cawfield Street in Grove Hall.

The best way to control the volume on streets is to make the street unappealing to thru traffic. Because Columbia Road is has a median, northbound cars cannot turn onto Eastman Street, which limits some of the traffic coming into the neighboorhood. Eastman is also a courtesy street, which means that, with parking, the road is wide enough for oncoming cars to pass each other, but they must slow down to make room. Courtesty streets also have no center line which allows drivers to stay to the middle of the road when there isn't oncoming traffic. This is safer for residents and bikers while forcing drivers to pay more attention. Painting lines makes drivers feel comfortable that, if they're in their lane, they don't have to worry about anything or anyone else. 

A car driving on Eastman Street. Driving down the middle of the street.

Furthermore, Cawfield and Elder Street are both one-way streets. This eliminates the usefulness of the neighborhood as a shortcut for traffic. The best way for volume control is a network of roads like this network. If you control several of the streets, but still leave a road cutting through that thru traffic can use, the vehicles will use that road and it will still be a dangerous neighborhood. This network is successful in application and upon speaking to a resident, she said that almost all cars that drive past her house are locals and live in the neighborhood.

St. Stephen Street is another good example of traffic calming. This one-way street adjacent to Northeastern campus carries traffic serving the University and residential traffic. Because the road is one-way, the volume is greatly limited to one direction. This still allows residents and students to use the street for their local needs, but eliminates the usefulness as a shortcut. While the road is fairly wide for a one-way street (approximately 35 feet), this includes plenty of room for parking on both sides as well as room to get around a double parked car. To make the drivers feel as though they are still on a small road, there are a lot of trees along the sidewalks to make it feel narrower. This also contributes a lot to the overall character of the street and makes a driver feel that they're in a residential/campus environment.

As with the courtesy street, on a one-way street, the vehicles tend to drive in the center of the road, leaving more room for bikes and peds, while slowing traffic and increasing awareness because drivers must pay attention to where they are in the road.
By limiting the dual parking lanes to residents only, the traffic volume is further limited to local traffic.

 All of these measures help calm the traffic and create a safe driving environment, but the most important aspect of traffic calming in this example are the places where traffic is forced to slow down or stop by way of stop signs and sharp turns.

As you can see, the block lengths are very short and there are stop signs at the intersections which bring traffic to a complete stop. This prevents a vehicle from building up much speed because it is uncomfortable for drivers to accelerate and brake quickly between stops. It is also uncomfortable and dangerous to go around corners quickly so having sharp turns on these roads also reduces speeds. The longest that a street goes in this neighborhood network without a stop sign or sharp turn is approximately 900 feet (or .17 miles).

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