Fast on the Freeway Can Lead to Fury on the Side Streets

New AAA Research Exposes the Crash Danger of Spillover Speeding

DEARBORN, Mich., (May 7, 2024) — Raising speed limits on highways could lead to more crashes on nearby roads, according to new research by the AAA Foundation for Traffic Safety. This "spillover effect" creates unintended safety hazards for local communities that might not be involved in the decision-making process to raise the posted speed limit on a nearby highway.  According to NHTSA, speeding is a significant safety concern, contributing to almost one-third of road fatalities in the past 20 years.

AAA Foundation researchers investigated whether changes to posted speed limits on interstate highways could cause drivers to adopt risky speeding behaviors on local streets. The study looked at crash data before and after speed limit increases on interstates in Georgia, Michigan, and Oregon. Hot spot analyses were conducted on roads within a 1-mile radius of interstates. Researchers found many instances where speed-related crashes increased on nearby roads following the interstate speed limit change, suggesting that drivers exiting the highway continued their faster tendencies.

“Although increasing posted speed limits may drive nominal improvements in traffic flow, it also creates unintended consequences in the surrounding community,” said Adrienne Woodland, spokeswoman, AAA – The Auto Club Group. “For one thing, higher speeds result in more severe traffic crashes. Additionally, this new research demonstrates that drivers will be moving faster when transitioning onto local streets, which are designed for slower speeds and diverse road users such as pedestrians and cyclists—not for speeding drivers."

AAA recommends a multi-pronged approach to combat speeding behavior:

By taking a proactive approach, transportation officials can create safer road networks for all communities. The AAA Foundation’s research reinforces the importance of the Safe System Approach (SSA). The SSA is a strategic way of leveraging the engineering and behavioral countermeasures proven effective at preventing traffic crashes and the injuries that can result from them. Explore the Foundation’s guide for implementing the SSA in your community HERE.

"This research has uncovered an unintended but potentially lethal consequence of raising highway speed limits," said Jake Nelson, AAA’s director of traffic safety advocacy. "With the U.S. near a record-high traffic death toll, road authorities can use these findings and an effective tool to pinpoint lifesaving solutions to help ensure that we all get home safely each day."

Previous speeding research by the AAA Foundation found that raising posted highway speed limits is associated with increased crash frequencies in some situations. At the same time, changes in travel times were small in response to both raised and lowered speed limits.

About the AAA Foundation

Established in 1947 by AAA, the Foundation for Traffic Safety is a nonprofit, publicly funded 501(c)(3) charitable research and educational organization. The AAA Foundation’s mission is to prevent traffic deaths and injuries by researching their causes and by educating the public about strategies to prevent crashes and reduce injuries when they do occur. This research informs the development of educational materials for drivers, pedestrians, bicyclists, and other road users.

About AAA - The Auto Club Group

The Auto Club Group (ACG) is the second largest AAA club in North America with more than 13 million members across 14 U.S. states, the province of Quebec and two U.S. territories. ACG and its affiliates provide members with roadside assistance, insurance products, banking and financial services, travel offerings and more. ACG belongs to the national AAA federation with more than 64 million members in the United States and Canada. AAA’s mission is to protect and advance freedom of mobility and improve traffic safety. For more information, get the AAA Mobile app, visit AAA.com, and follow us on Facebook, Twitter and LinkedIn.