Chicanes
Chicanes slow motorists through horizontal diversions.
Chicanes create a horizontal diversion of traffic and can be gentler or more restrictive depending on the design.
Diverting the Path of Travel
Shifting a travel lane has an effect on speeds as long as the taper is not so gradual that motorists can maintain speeds. For traffic calming, the taper lengths should reflect the desired speed which should be posted prior to the chicane.
Shifts in travelways can be created by shifting parking from one side to the other. This requires that there is only space for one side of parking or that there is parallel parking on one side and angle parking on the other (switch these two patterns back and forth, block to block). The other option is to build landscaped islands (islands can also effectively supplement the parking shift).
Lane Restriction (Angled Slow Points)
Restricting the lanes (as described under Chokers) usually consists of a series of curb extensions, narrowing the street to two narrow lanes or one lane at selected points and forcing motorists to slow down to maneuver between them. Such treatments are intended for use only on residential streets with low traffic volumes.
If there is no restriction (i.e., the number of lanes is maintained), chicanes can be created on streets with higher volumes, such as collectors or minor arterials.
Purpose
- Reduce vehicle speeds
- Add more green (landscaping) to a street
Considerations
- Chicanes may reduce on-street parking.
- Maintain good visibility by planting only low shrubs or trees with high canopies.
- Ensure that bicyclist safety and mobility are not diminished by not installing restricted lanes on steep uphill streets where bicyclists may be "pinched" while proceeding very slowly up a hill.
Estimated cost
Costs for landscaped chicanes are approximately $10,000 (for a set of three chicanes) on an asphalt street and $15,000 to $30,000 on a concrete street. Drainage and utility relocation often represents the most significant cost consideration.
