Study: Warm Weather Is a Factor in Increased Road Deaths

A downward trend in deaths from car crashes reversed sharply in 2015. Many blamed cell phones and the distractions they can cause, but a recent study complicates that hypothesis.

1 minute read

September 13, 2017, 6:00 AM PDT

By Casey Brazeal @northandclark


Crash

GUNDAM_Ai / Shutterstock

A study investigating deaths from car crashes found a correlation between warmer weather, vehicle miles traveled (VMT), and, ultimately, deaths on the road. Conducted by Dr. Leon Robertson, formerly of Yale University, the study found that 2015 was a particularly warm year in the U.S. and suggests this might be why it was such a deadly year on the streets. "Road deaths in the U.S. jumped 7 percent in 2015, to 35,200 — an abrupt reversal of the downward trend that has persisted for the previous 35 years," Susan Perry writes in the Minneapolis Post.

Robertson undertook the study in part because he was not convinced by the hypothesis that the jump in deaths was attributable to distracted drivers with cell phones. Robertson points out that by 2014 cellphones were already ubiquitous in the U.S.

"[Robertson] found that for each degree increase in temperature, vehicles were driven an average of 60 extra miles per person per year. He also found that for each additional inch of rainfall, vehicles were driven an extra 66 miles per person," Perry reports. Still, this study can only show correlation (not causation) between weather and driving, especially since the participants were not surveyed.

Friday, September 8, 2017 in Minneapolis Post

Young Professional

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban and Environmental Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban and Environmental Planner

Get top-rated, practical training for planners

"Planetizen federal action tracker" logo superimposed over black and white image of US Capitol dome.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

September 16, 2026 - Zachary Whalen

Passengers board an Amtrak train under a cloudy sky.

Amtrak, CN end decades-long dispute with eight-year agreement

The new operating agreement establishes an updated framework for the companies to work together, including processes to resolve disputes.

September 18, 2026 - Mass Transit

The Gross Reservoir, a large body of water surrounded by trees and mountains.

Judges permit Denver to divert 77,000 acre feet from the Colorado River for reservoir expansion

Overuse and climate change have caused the Colorado River’s water levels to plummet.

September 18, 2026 - Inside Climate News

A painted bus lane in NYC.

NYC DOT wants faster, more permanent street upgrades

The city is examining ways to build more concrete infrastructure without getting entangled in 'decades-long' projects.

September 21 - NYC Streetsblog

A woman looks at a utility bill.

'Something we’ve never seen before:' rising utility rates could strain city finances nationwide

Data centers, climate change and other factors have caused utility rates in the United States to increase by 38% since 2020.

September 21 - Smart Cities Dive

A person scuba diving in a coral reef off Guam.

Trump to overrule local leaders, lease millions of acres of America’s Pacific Island territories’ seafloors to mining companies

International law says that the Indigenous people of America’s territories have a right to prior and informed consent regarding projects that impact their countries.

September 21 - Grist