Tuesday, April 24, 2012

Courtesy Streets

by Michael Sarazen

Courtesy streets are two-way streets where vehicles have to make room for each other to pass. Parking can exist on one or both sides and pavement markings are rare. By not having enough room for two cars to pass, when there is an encounter in which two vehicles are approaching from opposite directions, one vehicle will pull off to the side of the road and allow the other vehicle to pass, hence the courtesy aspect of the street.

A narrower courtesy street
Higgins Street, Arlington MA

A wider courtesy street
Quincy Street approaching Mass Ave, Arlington MA

A typical curb-to-curb cross section of a courtesy street with parallel parking on both sides would be 26 to 30 feet. With 7 foot wide parking on both sides, this would mean a single 12 to 16 foot travel lane for both directions of travel. This width would easily allow a single vehicle on the road, but as it would allow for 6 to 8 feet per vehicle during an encounter, it would require one vehicle to stop and move to the right, either against the curb or into available parking while the passing vehicle is allowed to slowly pass around the stopped vehicle.

Encounter between a motorcycle and passenger car
Quincy Street approaching Mass Ave, Arlington MA

In terms of safety, courtesy streets act as a form of traffic calming, slowing traffic along a road by having these encounters. An encounter greatly reduces the speed of passing vehicles and discourages most cut-through traffic.

Encounter between two passenger vehicles from perspective of car pulled off to the side
Quincy Street approaching Mass Ave, Arlington MA
Google Maps Location

People are only willing to drive slowly for a limited amount of time and through a couple encounters. For this reason, courtesy streets are only used for roads intended to have low volumes. In order to keep volumes low, courtesy streets are often short, with larger streets intersecting them every few blocks and running parallel to them. This encourages drivers to use the larger streets as opposed to the smaller, more residential streets. This helps to make neighborhoods quieter, safer, and more enjoyable.

Low volume residential street
School Street, Arlington MA

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