As temperatures rise, pavement can soften or buckle, batteries can deteriorate more quickly, cooling systems work harder and tires face additional stress. If a vehicle fails, drivers can find themselves stranded beside fast-moving traffic in potentially dangerous temperatures. Research also points to an association between extreme heat and more severe crashes.
A new nationwide analysis from Attorney Brian White brings those risks together, examining where summer temperatures, road conditions and traffic exposure create the greatest combined problems for motorists.
The study ranks Arizona as the state with the highest heat-related road risk, with a score of 88.83 out of 100. Louisiana ranks second at 80.69, while Texas follows at 79.68.
But the ranking tells only part of the story. The underlying data show several ways extreme heat can turn an ordinary drive into a transportation-safety problem.
Hot Pavement Can Become a Road Hazard
Road infrastructure is designed to withstand wide temperature ranges, but repeated exposure to high heat can intensify existing weaknesses.
As pavement warms, materials expand and become more susceptible to deformation. Roads already weakened by moisture, age or heavy traffic may be particularly vulnerable.
Attorney Brian White’s study found major differences in pavement quality across the country.
Rhode Island had the nation’s highest share of poor pavement at 31.3%, followed by California at 27%, Massachusetts at 24.5%, New Jersey at 18.5% and New Mexico at 18.2%.
| State | Share of Poor Pavement |
|---|---|
| Rhode Island | 31.3% |
| California | 27.0% |
| Massachusetts | 24.5% |
| New Jersey | 18.5% |
| New Mexico | 18.2% |
| Louisiana | 16.1% |
| Texas | 7.3% |
Poor pavement alone does not make a state especially vulnerable to heat-related driving problems.
Rhode Island ranks only 29th on the overall index because its summer temperatures are much less extreme than those found in the South and Southwest.
California presents a different situation. The state ranks among both the five highest overall heat-risk states and the five states with the largest poor-pavement shares, creating an overlap between temperature exposure and existing road vulnerability.
Louisiana demonstrates the same interaction. Its 16.1% poor-pavement share helped push it ahead of hotter Texas in the overall ranking.
Road Damage Has Already Appeared During Houston Heat
Drivers in Houston have seen what high temperatures can do to road surfaces.
During a two-week stretch of extreme temperatures, TxDOT reported heat-related damage on at least 10 Houston-area roadways. Incidents included an entrance ramp to Interstate 10, Highway 6 near Alvin and a section of Highway 146 in Baytown that required emergency repairs.
That local example reflects a larger infrastructure concern across Texas.
Attorney Brian White’s study reports that TxDOT classified 788 road miles in its Laredo District as highly vulnerable to extreme heat, representing more than half of all Texas roadway mileage receiving that designation.
Potential impacts identified in the analysis include:
- Pavement rutting
- Surface cracking
- Road buckling
- Emergency repairs
- Temporary closures
- Traffic detours
- Disruptions to transportation systems
Laboratory and modeling research provides another indication of how pavement can respond to rising temperatures. One study cited in the analysis found modeled rut depth doubling from approximately 4 millimeters to 8 millimeters as pavement temperature increased from 34°C to 49°C. At 63°C, the modeled rut depth approached 13 millimeters.
Arizona Faces the Most Persistent Extreme Heat
The road problem becomes more significant in states where extreme temperatures persist for much of the summer.
Arizona recorded the highest average summer maximum temperature in Attorney Brian White’s analysis at 95.79°F.
It also had:
- 80 statewide days at or above 90°F
- 21 statewide days at or above 100°F
- The highest overall Heat-Related Driving Risk Index score at 88.83
Texas had the country’s second-highest average summer maximum at 93.45°F and recorded 78 days reaching at least 90°F. Texas and Mississippi also experienced the longest uninterrupted stretch of 90°F-plus conditions, lasting 43 days.
Florida recorded an average summer maximum of 92.07°F, 76 days of at least 90°F and a 35-day continuous stretch above that threshold.
At the cooler end of the ranking, North Dakota received the lowest overall risk score at 13.56, followed by Minnesota at 13.67 and Wyoming at 18.56.
Those differences matter because exposure is cumulative. A single hot afternoon can place stress on a vehicle or roadway, but weeks of sustained high temperatures provide far less opportunity for pavement, mechanical systems and drivers to escape those conditions.
Batteries and Breakdowns Add Another Summer Risk
Heat can also attack the vehicle itself.
AAA recorded more than 27 million emergency roadside service calls in the United States during 2024. Approximately 13 million required towing and another 7 million involved battery problems, meaning those two categories accounted for roughly 74% of all calls.
Those figures are not limited to summer or heat-related failures, but AAA identifies battery problems, engine trouble and flat tires among the mechanical issues likely to disrupt summer travel.
High temperatures can accelerate battery degradation and place additional pressure on cooling systems. The risk is especially important during extended heat waves because the same temperature conditions affecting the vehicle continue after a driver becomes stranded.
A breakdown that occurs on a 75°F day and one that occurs during prolonged 100°F conditions are mechanically similar events, but they can create very different exposure for the people inside the vehicle.
Tire Problems Killed More Than 500 People in 2024
Tires are another point where weather, maintenance and highway safety intersect.
The National Highway Traffic Safety Administration recorded 511 fatalities in tire-related crashes during 2024.
Those fatalities are not classified as heat-specific. Still, high temperatures can accelerate tire deterioration, particularly when tires are underinflated, worn or otherwise poorly maintained.
NHTSA warns that inadequate tire maintenance can result in:
- Flat tires
- Blowouts
- Tread separation
- Reduced vehicle control
Those issues can become particularly dangerous at highway speeds.
Heat can also affect vehicle efficiency. Testing cited by Attorney Brian White found that at 95°F, battery-electric vehicle efficiency fell by 10.4% and driving range declined by 8.5% compared with a 75°F baseline. Hybrid fuel economy fell by approximately 12%.
The effect does not necessarily create a direct crash hazard, but it illustrates how extreme temperatures influence multiple vehicle systems at once.
A Breakdown Can Become More Dangerous Once Occupants Leave the Car
Vehicle failure is not always the end of a road emergency.
AAA Foundation research using federal crash data found that more than 2,100 people were killed outside disabled vehicles along roadsides between 2019 and 2023. Victims included motorists, emergency personnel, roadside-assistance workers and people who stopped to help.
The roadside deaths were not heat-specific, but they reveal an important secondary danger.
When a battery fails, a tire blows or another mechanical problem forces a vehicle to stop, drivers and passengers may be placed near active traffic. Extreme temperatures can further complicate that decision by making it difficult to remain safely inside an unpowered vehicle.
In that sense, heat-related vehicle problems can create a chain of exposure:
- High temperature places additional strain on a vehicle.
- A mechanical problem forces the driver to stop.
- The occupants must decide whether to remain in a hot vehicle or exit near traffic.
- Roadside exposure creates another collision risk.
Attorney Brian White’s analysis treats that interaction as an important part of understanding why heat-related transportation problems extend beyond mechanical repair costs.
Extreme Temperatures Are Associated With More Severe Crashes
Heat may also affect what happens before a vehicle breaks down.
A 2026 study included in Attorney Brian White’s analysis examined more than 1.4 million crashes across 177 California cities.
At temperatures in the 99th percentile, researchers found the relative risk reached 1.35 for severe crashes and 1.22 for fatal crashes. Elevated risks were particularly noticeable for crashes involving pedestrians and bicyclists, and the relationship between heat and crash risk was more pronounced at intersections.
The findings do not establish that heat caused individual collisions. Driver behavior, traffic conditions, roadway design and many other variables also influence crash outcomes.
Another U.S. study referenced by Attorney Brian White reported a 3.4% increase in fatal traffic crashes on heat-wave days compared with similar non-heat-wave days.
Together, the research suggests that extreme heat should be considered alongside more familiar traffic-safety concerns rather than viewed only as a weather condition.
Road-Surface Heat Can Cause Serious Injuries Outside a Vehicle
In some places, pavement itself can become dangerous enough to cause severe burns.
During June through August 2023, an Arizona burn center treated 136 patients for severe pavement-contact burns, according to data highlighted in the Attorney Brian White study.
Fourteen patients died, 34% required intensive care and many required skin grafting or multiple surgical procedures.
The injuries illustrate what can happen when a crash, fall, medical emergency or other incident leaves a person in direct contact with extremely hot pavement.
For pedestrians, bicyclists, motorcyclists and people involved in roadway incidents, the road surface can therefore become another hazard during extreme temperatures.
The Most Heat-Vulnerable States Also Have More Traffic Exposure
Attorney Brian White’s study found a clear gap between states at opposite ends of its index.
The 10 highest-risk states averaged 63.8 days at or above 90°F, compared with just 4.5 days among the bottom 10.
They also had more heavily used roads.
The top 10 averaged 443,614 vehicle miles traveled per lane-mile, compared with 197,252 among the 10 lowest-ranked states. That means traffic exposure was more than twice as high in the top group.
New Jersey recorded the highest individual traffic exposure at 937,163 VMT per lane-mile, followed by Florida at 891,656 and California at 821,885.
| State | VMT per Lane-Mile |
|---|---|
| New Jersey | 937,163 |
| Florida | 891,656 |
| California | 821,885 |
| Maryland | 795,063 |
| Massachusetts | 794,675 |
| Texas | 436,026 |
New Jersey ranks only 18th overall, however, demonstrating again that traffic exposure alone does not determine heat-related road risk.
Crashes and Infrastructure Damage Carry Significant Costs
The consequences can also extend to household and public budgets.
The National Safety Council estimates that a property-damage-only crash carried an average economic cost of $6,600 per damaged vehicle in 2024. A disabling injury averaged $174,000 in economic costs, while a motor-vehicle death was estimated at $2.05 million.
Those figures represent crashes generally, not collisions caused by heat.
Vehicle operating costs can also rise during hot conditions. Data highlighted by Attorney Brian White found that operating at 95°F added approximately $6.78 per 1,000 miles for an electric vehicle charged at home, $16.25 when using commercial charging and $13.02 for a hybrid vehicle.
At the infrastructure level, one national pavement analysis projected that rising temperatures could create approximately $19 billion in additional U.S. pavement costs by 2040 under a moderate warming scenario, with the estimate increasing to $26.3 billion under a higher-warming scenario.
How Attorney Brian White Calculated the Road-Heat Risk Index
Attorney Brian White’s index uses six equally comparable state-level measures representing heat exposure, road use and infrastructure condition.
| Measure | Weight |
|---|---|
| Average summer maximum temperature | 20% |
| Days reaching at least 90°F | 20% |
| Days reaching at least 100°F | 15% |
| Longest continuous 90°F-plus period | 15% |
| Vehicle miles traveled per lane-mile | 15% |
| Poor pavement share | 15% |
Temperature measurements cover June through August 2025, while road conditions and traffic exposure rely on 2024 highway data.
Each state was scored relative to the others before the six measures were combined into the final index. Alaska and Hawaii were excluded because comparable finalized statewide climate data were not available for the required measures.
The index measures relative exposure and infrastructure vulnerability. It does not estimate the probability that an individual driver will crash, suffer a tire failure or experience a breakdown.
The distinction is important, but so is the overall pattern.
Arizona ranks first because few places combine such persistent, intense summer heat with substantial driving exposure. Louisiana’s existing pavement conditions push it into second place, while Texas combines some of the country’s most sustained heat with documented road damage and a large transportation network.
Attorney Brian White’s findings show that extreme heat can affect nearly every part of a trip. It can begin beneath the tires as pavement deteriorates, continue inside the vehicle as mechanical systems face additional stress and become a roadside safety issue if something fails.
For drivers, that makes extreme heat more than a number on a weather forecast. It is increasingly another condition affecting how safely America’s roads, vehicles and transportation systems operate.
