Curb Extensions and Modifications
Purpose
Shorten crossing distances, reduce vehicle turning speeds, improve visibility and sight distance, and increase pedestrian comfort at intersections.
Description
A wide curb radius allows drivers to turn right at high speeds and increases risk of collisions with pedestrians. Reducing the corner radius encourages drivers to slow down to take a sharper turn. Reducing the corner radii also reduces crossing distance for pedestrians and provides flexibility for curb ramp placement. Corners can be modified by adding curb extensions or truck aprons.
- Curb extensions can be implemented either (1) with pavement markings or flex posts for a low cost, temporary solution, or (2) using concrete to permanently convert the space to sidewalk area.
Safety Benefits
- Shorten crossing distance.
- Increase visibility between drivers and pedestrians.
- Narrow the roadway to reduce through vehicle speeds.
- Reduce vehicular turning speed.
- Prevent drivers from parking near or on the crosswalk.
- Expand waiting areas for pedestrians waiting to cross.
Street Types and Context
Applicable Street Types
All street types.
Other Location Guidance
Curb modifications can be made everywhere from a mid-block crosswalk to a large, signalized intersection. Curb extensions can be built in all-day parking lanes or wide shoulders.
Primary User Groups
Key Implementation Considerations
- Curb modifications should not extend into travel lanes or bicycle lanes.
- Travel lane or turn lane removal or narrowing must be analyzed prior to considering using this tool to accommodate a smaller curb radius.
- Curb extensions can be used at intersections with low truck or bus volumes. The goal should be to make the intersection as compact as possible while still allowing larger vehicles to navigate the turns.
- Corner radii that are too small may encourage vehicles to drive over the curb and onto sidewalks or raised bikeways.
- Curb extensions can require modifications to or relocation of drainage structures.
- A longer timeframe may be needed if curb modifications are included in a capital or redevelopment project.
Expected Crash Reduction
Nearly 50% based on engineering judgement. A CMF has not yet been determined; initial research indicates this treatment may be effective at increasing driver yielding and improving pedestrian safety (Johnson et al. 2005; Thomas et al., 2016).
Cost
Costs vary depending on design, site conditions, and materials. Designs with only markings and/or flexible delineator posts are lower-cost alternatives but require ongoing maintenance.
Timeline
Less than one to three or more years, depending on complexity.
References
