Reduced Corner Radii

A large turn radius allows drivers to make higher speed turns and increases the crossing distance.

There is a direct relationship between the size of the curb radius and the speed of turning motor vehicles. A large radius may easily accommodate large fire trucks and other large trucks and school busses, but it also allows other drivers to make high speed turns and it increases the crossing distance for pedestrians. Motorists who drive faster are less likely to stop for pedestrians. A larger radius will also result in a longer crossing distance for the pedestrian. The solution is to reduce the curb radius.

When designing curb radii, consider what motor vehicles actually need when turning. Instead of assuming that every corner needs to be cut back, look at other factors such as on-street parking and bicycle lanes to determine how much space a turning motor vehicle will need. The effective radius that exists should include the width of parking lanes and bicycle lanes on both streets. Large trucks do not need to stay on their half of the street when turning on local streets. There is not a need to design for the largest vehicle that may use a street, especially for streets inside neighborhoods.

The effective radius that exists should include the width of parking lanes and bicycle lanes on both streets.

Treatment: Reduced Corner Radius


The reduction of a corner radius to produce a tighter turn results in decreases in turning speeds and improved motor vehicle and pedestrian site distances, and a shortened pedestrian crossing distance.

Expected Effectiveness

  • Reduces the most common type of pedestrian crash by decreasing right-turn motor vehicle speeds.
  • Shortening of crossing distance can improve signal timing and reduces the exposure of pedestrians to motor vehicles.


Costs range from $2,000 to $20,000 depending on drainage, utilities and other site features [PEDSAFE, 2004].

Keys to Success

  • The needs of all road users including pedestrians, bicyclists, buses, trucks and cars needs to be considered in designing or retrofitting corner turn radii.
  • Appropriate design based on street type, angle of intersection, land uses, etc. should also be considered.

Key Factors to Consider

  • Designing for maintenance vehicles, emergency vehicles and school buses. Pedestrians are at risk if large vehicles ride over the curb.

Evaluation Measures

  • Right-turning motor vehicle pedestrian crashes.
  • Total pedestrian crashes.