Reducing Speeding-Related Crashes Through Design

September 26, 2017

According to the National Transportation Safety Board (NTSB), speeding is one of the most common factors in motor vehicle crashes in the US. The NTSB reported that more than 112,500 people died in speeding-related US highway crashes from 2005–2014. Speeding is the cause of 10,000 deaths on US roadways each year.

High speeds have especially serious consequences for people walking and biking.


People walking and biking are less likely to survive a crash at higher speeds.

Graphic from LADOT Vision Zero.

A study by the Governors Highway Safety Association (GHSA) found that in 2015, 720 bicyclists were killed and 45,000 bicyclists — 12,000 youth and 33,000 adults — were injured on US roadways. The GHSA also reports that the number of pedestrian fatalities in the United States increased by 25 percent from 2010 to 2015. According to a National Highway Traffic Safety Administration report, there were 5,376 pedestrian fatalities involving traffic crashes in 2015.





A Systemic Approach to Safety

The foundation for reducing speeding-related crashes is setting and designing to a target speed that is appropriate for the context. Our job as transportation professionals is not to defend past practices (i.e. how a street was previously designed or how to set speed limits), it is our job to evolve our practices to reflect the new societal needs/cultures, new environments, changes in land uses, or changes in a community or corridor. It is our duty to re-evaluate all the factors, which often times warrants new approaches to address the complex needs of today.

Designing “self-enforcing” streets that force people driving to slow down and pay attention to their surroundings is critical to reducing speeding-related crashes.

Reducing Speeds Through Design

Better bicycle infrastructure, traffic calming, and lower speed limits have great potential for reducing bicycle and pedestrian injuries and fatalities. Better street design includes improved intersection crossings, reduced street crossing distances, making people walking more visible, and slowing turning vehicles.


The Memphis Medical District Streetscape Improvement project involved narrowing of existing wide streets to make room for people walking and biking, reduce crossing distance at intersections, and slow the movement of turning vehicles.


The Alta-designed cycle track in Lincoln, Nebraska, includes protected intersections through geometry, signal separation at intersections, set back driveways, and two-stage turn boxes for comfortable turns from the separated bikeway.


Median refuge areas and curb extensions improve visibility and reduce crossing distances for people walking.

Local roads have three times as many traffic deaths as highways. The best work to reduce vehicle speeds can be done at the local level, where communities can be bold and innovative.

Tools Communities Can Embrace to Reduce Fatal Crashes

Complete Streets

“Complete Streets” provide facilities for all users; this is especially important on suburban arterials with high speeds and car-centric design. Complete Streets create opportunities for people to choose how they move through a community, while enhancing the function and character of a street through traffic calming, streetscape elements, and green infrastructure.


Rendering by Alta Planning + Design.

Traffic Calming

Traffic calming causes drivers to slow down by constricting the roadway space or by requiring careful maneuvering. Traffic calming can also lower vehicle volumes by physically or operationally re-configuring corridors and intersections.

Example traffic calming treatments include:


Traffic Circles. Traffic circles reduce conflict potential and severity while providing traffic calming to the corridor.


Chicanes. Chicanes form an “S”-shaped curb, which reduces vehicle speeds by requiring motorists to shift laterally through narrowed travel lanes. (Photo on left via Richard Drudl, photo on right via Dan Burden pedbikeimages.)


Textured pavement emphasizes a change in environment to a residential street and is thought to increase driver awareness.


Curb Extensions and Pinchpoints. Extending the curb into the parking lane at intersections reduces pedestrian crossing distances and improves visibility between motorists and people walking. Pinchpoints are wider than normal curb extensions and placed on both sides of the street, narrowing the travel lane and encouraging all road users to slow down. When placed at intersections, pinchpoints are known as “chokers” or “neckdowns.”


Raised Crosswalks. Raised crosswalks are elevated, marked pedestrian crossings above street grade at intersections or mid-block. Renderings by Alta Planning + Design.

Roundabouts

Compared to stop-controlled and signalized intersections, roundabouts can reduce crashes where people are seriously hurt or killed by 78–82%. Additionally, emissions are lower because cars don’t need to accelerate from a complete stop.

— Alta Planning + Design (@altaplanning) August 14, 2017

Fewer and Narrower Lanes

Four-lane undivided highways experience relatively high crash frequencies. A roadway reconfiguration known as a “road diet” offers several high-value improvements at a low cost. Resulting benefits of a road diet have shown to include a crash reduction of 19 to 47 percent, reduced vehicle speed, and improved mobility and access for all road users.


Example of a “road diet.” Rendering by Alta Planning + Design.

High Visibility Crosswalks

Including additional paint enhances a motorist’s awareness of a crosswalk. Near schools, crosswalks should be painted for additional visibility. In roadway lighting can further enhance crosswalk visibility. Crossing Beacons like the ‘Rectangular Rapid Flash Beacon (RRFB)’ can enhance the visibility of crosswalks marked by just paint. Flashing lights and additional signage alert motorists to the presence of crosswalks and pedestrian traffic.

Update: FHWA Rescinds Interim Approval for RRFBs


Renderings by Alta Planning + Design.

Temporary, “tactical” crosswalk outside of a school in Coalinga, CA.

Contributors:
Paula Flores, FITE, Principal, Alta Planning + Design
Bryan Jones, PE, AICP, Principal, Alta Planning + Design

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