Getting caught in a standstill on a busy interstate is one of the more frustrating realities of highway travel. Whether traffic has frozen because of a crash miles ahead, a construction bottleneck, or a chain of slow-downs during rush hour, drivers often find themselves wondering whether sitting still inside the car is really the best option.
The answer depends on several environmental and traffic-flow factors, but the general guidance from transportation agencies across the country leans strongly toward staying put. The roadway environment itself is the biggest reason why. Even in congested conditions, the speed differential between a standing person and a vehicle that suddenly accelerates is substantial enough to be dangerous.
Why Highways Create a Specific Risk for People Outside Vehicles
Not all roads carry the same risk when a person exits their car. A residential street with low traffic and sidewalks is a very different environment from an interstate with four lanes, minimal shoulder space, and vehicles merging or braking unpredictably.
The Connecticut Department of Transportation put it plainly in a 2025 public safety reminder: highways are designed for vehicles traveling at high speeds, and even a brief moment outside a car can have deadly consequences. That guidance was aimed at breakdowns, but the same physical reality applies during a traffic jam. Congestion doesn’t eliminate the hazard, it redistributes it, as drivers in moving lanes may not see a pedestrian standing in an adjacent stopped lane.
The Problem of Secondary Crashes
One of the less-discussed dangers in a traffic backup is the secondary crash — a collision that occurs not because of the original incident, but because of the queue it creates. The Federal Highway Administration defines a secondary crash as one that occurs either within the original crash scene or within the backup it generates in either direction. These events can happen on any type of roadway, and the primary incident doesn’t need to block lanes or involve serious injuries to trigger one.
When a driver stands outside their vehicle in a stopped queue, they are exposed to exactly the kind of scene where a secondary crash is plausible. A distracted or drowsy driver approaching the back of the jam may not react in time, and a person outside a vehicle has no protection at all from an impact.
Environmental Factors That Change the Calculus
Extreme Heat
On summer highways in states like Texas, Arizona, or Florida, sitting in a running vehicle during a long delay can raise interior temperatures — especially if the air conditioning is not functioning. It is recommended that drivers stuck in traffic while idling should partially open a window to ventilate the cabin. That simple step addresses heat buildup without requiring anyone to leave the vehicle.
If the engine is running and the air conditioning is working, the inside of the car remains far cooler than standing on exposed asphalt in direct sun, where radiated heat from the road surface adds to ambient temperatures.
Carbon Monoxide in Heavy Traffic
Prolonged idling in bumper-to-bumper traffic does raise one concern: carbon monoxide accumulation. Vehicle exhaust on congested roadways and busy intersections can elevate ambient CO levels beyond what fixed-site monitors measure. The Pennsylvania Department of Transportation recommends cracking a window while idling to allow adequate ventilation without requiring anyone to step outside. Stepping out into lane traffic is not a solution to CO concerns, and the exposure risk from brief idling in open-air traffic is considerably lower than it would be in an enclosed space like a tunnel or parking garage.
Winter and Wet Conditions
In icy or snowy conditions, the same physics that make highways slippery for vehicles make them dangerous for pedestrians. Visibility drops, stopping distances extend, and surfaces offer poor traction. Standing outside on an icy highway shoulder with limited sight lines from other drivers is a combination that creates real exposure. If stranded in winter weather, state transportation agencies generally recommend staying inside, running the heater intermittently, and keeping the exhaust pipe clear of snow to prevent CO buildup in the cabin.
Traffic-Flow Reasons to Remain in the Vehicle
Beyond personal safety, staying in the vehicle contributes to smoother traffic flow during a jam. When drivers park and exit, they effectively abandon a lane or shoulder position, which can block emergency responders trying to reach the scene ahead and further restrict the movement of other vehicles through the congested zone.
Traffic incident management directly affects how long secondary crash risk windows remain open. The FHWA has long tracked secondary crash patterns as a major concern in traffic operations precisely because queues behind incidents are where exposure concentrates. Keeping vehicles occupied and ready to move forward as lanes clear reduces the duration of those exposure windows.
When It Might Be Necessary to Exit the Vehicle
There are narrow circumstances where leaving the vehicle becomes appropriate or unavoidable:
- Active fire or smoke from the vehicle itself — if the car is burning, immediate exit and distance from the vehicle is warranted.
- Rising floodwater — if water is entering the vehicle and continuing to rise, exiting quickly (using the window if the door won’t open against water pressure) is the recommended response, per ready.gov guidance on floods.
- Medical emergency — if a passenger requires immediate assistance and emergency responders cannot reach the scene quickly, limited, careful movement to the shoulder may be necessary.
In each of these cases, the decision is driven by a hazard inside or immediately surrounding the vehicle, not by discomfort or boredom during a routine delay.
How These Incidents Appear in Accident Reports
When a pedestrian is struck on a highway during or near a traffic jam, local accident reports typically categorize the incident by the nature of the roadway, the lighting conditions, and whether the person was in a travel lane, a shoulder, or an unmarked area. Secondary crash designations have been added to traffic crash reporting forms in a growing number of states.
Reports from highway corridors consistently show that pedestrian vulnerability increases in low-visibility conditions, at night, and at locations where drivers cannot anticipate a person standing outside a stopped vehicle. These details appear in both state police reports and local traffic monitoring systems.
FAQ
Is it ever safe to get out of the car on a highway during stopped traffic?
In most situations, the answer is no. The risks from passing vehicles, limited shoulder space, and low visibility outweigh the discomfort of waiting inside the car. Even a brief moment outside a vehicle on a highway can have serious consequences. The exception is when a hazard inside or immediately around the vehicle makes staying inside a greater danger.
What should drivers do about heat while stuck in highway traffic?
Running the air conditioning is the most effective option when the engine is on. If heat becomes a concern while idling, cracking a window provides ventilation without requiring anyone to exit.
How does carbon monoxide risk factor into staying in an idling car during a traffic jam?
Outdoor, open-air traffic jams do not produce the enclosed conditions that cause dangerous CO buildup. The risk is greatest in tunnels, enclosed parking garages, or vehicles with damaged exhaust systems. In open-air highway conditions, cracking a window during a long idle is sufficient to address any minor buildup, and this approach is endorsed by state transportation agencies as a practical precaution.
Stay Informed About Highway Conditions Before You Travel
Road conditions on major interstates and state highways can change quickly — a minor fender-bender can become a multi-mile backup within minutes, and a weather event can shut down stretches of road without much warning. Monitoring real-time traffic updates before and during a trip helps drivers anticipate delays and avoid the situations where these decisions arise at all.
Local Accident Reports shares updates on traffic incidents, road closures, and crash-related conditions across highways and local roads nationwide. Checking current reports before heading out on congested corridors can make a meaningful difference in how prepared drivers are when conditions change ahead.
Visit our website to stay updated on traffic incidents or call our team at (888) 657-1460 to learn more.
