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FHWA Highway Safety Programs

Lower Citywide Speed Limits and Design Changes

fhwasa2213.pdf (1.35 MB)

Lower Citywide Speed Limits and Design Changes: Safer city arterials for all road users

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Excessive speeding in cities can be particularly deadly for vulnerable road users, especially on busy arterials with high volumes of vehicle, pedestrian, and bicycle interaction. Only five out of 10 pedestrians will survive a crash with a vehicle traveling at 42 miles per hour (mph).1Graphic reads: Safe Speeds: Reducing Pedestrian Fatalities. Hit by a vehicle traveling at 23 MPH - 10% risk of death. Hit by a vehicle traveling at 42 MPH - 50% risk of death. Hit by a vehicle traveling at 58 MPH - 90% risk of death..

Source: FHWA based on AAA study1

Transportation practitioners use a variety of strategies to manage speed, and lowering speed limits citywide is one of those strategies. However, simply lowering the citywide speed limit isn't always enough to slow drivers—a wide travel lane design and unobstructed views on many city arterials encourage speeding by making drivers feel that it is safe to speed.

Redesigning City Arterials

Many cities incorporate countermeasures into street design to reduce vehicle speeds and contribute to a complete streets environment—one that enhances the safety and mobility of all road users. Examples include:

Raised Pedestrian Crosswalks

Photo shows a crosswalk on a raised section of asphalt.

Source: SDOT, Rasied crosswalk,

Often installed at mid-block crossings, raised pedestrian crosswalks extend across the entire width of the roadway. Pedestrians cross at the same level as the sidewalk, making them more visible to drivers. Approach ramps cue drivers to slow down, giving them more time to react near pedestrians.

Lane Reduction

Photo shows a crosswalk on a raised section of asphalt.

Source: FHWA

Lane reduction reduces the number of travel lanes on a multilane undivided roadway, which can affect a driver's choice of speed. Also known as a road diet, the extra space can be reallocated to add dedicated turn and bus lanes and other countermeasures such as pedestrian visibility and crosswalk enhancements.

Curb Extensions

Photo shows a street with walkways and extended curbs between walkways and the road.

Source: FHWA

Curb extensions reduce the width of the roadway by extending the curb into the parking lane. This shortens pedestrian crossing distances and reduces the time needed to cross the street. Drivers are encouraged to slow down when approaching intersections and mid-block crossings, making turns, and traveling through intersections.

Lane Narrowing

Photo shows a lane that reads 25 MPH and has pavement markings between the lane and the curb to show a narrower lane width.

Source: FHWA

Lane narrowing using pavement marking techniques reduces the width of the travel lane. It frees up space for traffic calming measures such as widened sidewalks, extended curbs, and chicanes. Also called a lane diet, this can force slower vehicle traffic, make drivers more aware of surroundings, and give drivers more time to react to pedestrians at intersections and crosswalks.

Spotlight on Seattle: Redesigning a Crash-Prone Arterial

After lowering the citywide speed limit from 30 to 25 mph, excessive speeding on Rainier Avenue South was still a challenge. Seattle Department of Transportation employed street design changes to help improve speed limit compliance and road user safety on Rainier Avenue South.


  • Reduce excessive speeding
  • Increase compliance with reduced citywide speed limit
  • Reduce number and severity of injuries from collisions


  • Removed one lane of traffic in each direction
  • Added dedicated bus lanes and center turn lanes
  • Narrowed travel lanes with curb and sidewalk extensions
  • Improved signage for better visibility of lowered speed limit


  • 52% decrease in speeding northbound; 28% decrease southbound
  • 15% decrease in collisions overall
  • 30% decrease in injury collisions
  • 40% decrease in pedestrian and bicycle collisions

* Source: SDOT, Rainier Avenue South Safety Corridor: Rainier Pilot Project Evaluation.

Photo shows a four lane road with two yellow lines in the middle.


Photo shows the same road as Before, but with one lane heading in each direction, an extended median, extended curbs, and a two-way left turn lane.


Source: Seattle Department of Transportation

"Redesigning Rainier Ave S to be self-enforcing and adding speed management countermeasures has improved compliance with the lowered posted speed limits."
–Jame Le, SDOT

Learn More

1 AAA Foundation for Traffic Safety, Impact Speed and a Pedestrian's Risk of Severe Injury or Death (Washington, DC: 2011). [ Return to note 1. ]


Page last modified on December 27, 2021