Overpass Shelter During Storms (Highway Safety Risks)
A highway overpass is not a designated storm shelter. During a storm, do not stop, park, or take refuge beneath it or on a highway shoulder. Move to a substantial enclosed building or an officially designated shelter when you can do so safely. Follow local alerts, and wait at least 30 minutes after the last thunder before resuming outdoor activity.
If storms are part of your regular travel, a little planning can save time, reduce stress, and offer better value than reacting at the last moment. Check alerts before you leave, know where a designated shelter is, and plan a safe route to it. Concrete and apparent size do not prove that an overpass can protect people from wind, debris, lightning, or flooding.
I treat the decision as a sequence: identify the hazard, avoid traffic and flood risks, reach a suitable shelter, then wait for the official all-clear. These steps apply whether you are driving, walking near a highway, or waiting at an event. If you cannot reach a shelter safely, follow instructions from local emergency officials.
Planning: Identify the Hazard and Official Shelter
A designated shelter is a place that the responsible authority has identified for use during a particular emergency. Before travel, check the current forecast and local alerts, then find out which shelter is open and how to reach it. An overpass does not become a shelter just because it looks strong.
Different storms create different hazards. Lightning calls for a substantial enclosed building or a hard-topped vehicle. Tornadoes and severe winds call for a suitable building or purpose-built storm shelter. Flooding calls for moving away from low areas and rising water. A route that works for one threat may be unsafe for another.
What makes a shelter suitable?
A storm shelter is a space designed or designated to protect people from a defined hazard. FEMA P-361 gives guidance for safe rooms, while ICC 500 sets design and construction criteria for purpose-built storm shelters. Neither standard certifies an ordinary highway overpass as a shelter.
The important word is “designated.” Ask local emergency management, venue staff, or another responsible authority whether a site is open, accessible, and intended for the current hazard. Do not infer its status from concrete walls, a roof, or its location below road level. Shelter capacity and access can vary by site.
There is no universal underpass clearance, airflow rate, occupant limit, or hardware rating that makes an overpass safe as a public storm shelter. Those questions depend on the structure, its setting, the hazard, and applicable codes. Without a formal assessment and designation, the safe choice is not to use it as refuge.
A quick planning check
Before setting out, I would check:
- The storm type and current warnings for the route.
- The nearest designated shelter and whether it is open.
- Whether the route to it is accessible and away from highway traffic.
- Whether flooding may affect the shelter or route.
- Any evacuation, road closure, or shelter instructions from local officials.
For value for money, this simple check can prevent avoidable delays and help you choose a route before conditions worsen. It also avoids relying on a structure that may not offer the protection you need. Keep the plan flexible: severe weather can close roads or change which shelter is safest.
Access and Clearances: Stay Out of Traffic and Flood Zones
A clearance is the safe space needed to reach and use a shelter without entering a traffic lane, restricted area, or hazard zone. There is no general “safe distance” that makes it acceptable to walk or wait on a highway shoulder or beneath an overpass. Use a route approved for pedestrians.
An overpass may look like a quick escape from rain or wind, but it can expose you to moving vehicles and debris. Wind can be redirected or intensified around structures. A low underpass can also collect water quickly. Its concrete construction does not show that it has been tested or built to protect occupants in a storm.
If you are driving
If caught driving in a storm, do not stop beneath an overpass or on a highway shoulder to wait it out. Continue toward a substantial building or designated shelter when it is safe to do so, and follow road closures and official directions. Do not drive through floodwater; water depth and road condition can be hard to judge.
If visibility or road conditions make continued driving unsafe, use official guidance and seek a safe place that is not the shoulder, bridge, or underpass. Contact emergency services if there is an immediate threat or you are unable to reach safety. Avoid making sudden moves that put you or others in traffic danger.
The Manual on Uniform Traffic Control Devices (MUTCD) covers traffic-control devices and work zones. It does not grant permission for pedestrians to occupy a highway shoulder, bridge, or underpass as a storm refuge. A closed lane or work area is not a public shelter unless the responsible authority specifically says it is.
If you are on foot
Do not enter a roadway, bridge, or restricted area to reach an overpass. Look for the nearest open building or officially designated shelter using a safe pedestrian route. If the route is blocked, follow local emergency instructions rather than attempting to cross traffic or walk through floodwater.
| Situation | Safer action | Avoid |
|---|---|---|
| Lightning nearby | Enter a substantial enclosed building or hard-topped vehicle | Open-sided shelters, isolated structures, and overpasses |
| Tornado or severe wind warning | Use a designated storm shelter or suitable building as directed | Waiting under a highway bridge or in a vehicle near traffic |
| Water rising near a low point | Move to higher ground by a safe route and follow alerts | Walking or driving through floodwater or waiting in an underpass |
| Road closure or evacuation | Follow signs and official instructions | Entering closed roads, shoulders, or work zones |
These are general actions, not a substitute for local instructions. Conditions differ by place and storm type. When alerts conflict with a planned route, follow the current directions from emergency officials.
Execution: Move to a Designated Enclosed Shelter
A substantial enclosed building is a solid, fully enclosed structure that offers protection from the outside environment. When lightning threatens, the National Weather Service advises people to go to a substantial building or a hard-topped vehicle. An open-sided shelter does not provide the same protection.
The safest action depends on the hazard. For lightning, get indoors or into a hard-topped vehicle as soon as possible. For tornado or severe wind danger, use a designated storm shelter or follow local advice on where to shelter in a sturdy building. For flood risk, move away from low ground and rising water. Do not assume one shelter choice covers every threat.
Step-by-step decision sequence
- Survey the situation. Identify the hazard from current official alerts. Find the nearest designated shelter, a safe route, and any flood or traffic restrictions. Do not enter the highway or bridge structure to inspect it.
- Check access. Follow evacuation and shelter instructions. Confirm that the facility is open if that information is available. If your route is blocked, use another safe route or follow instructions from local officials.
- Move promptly. If driving, do not stop beneath an overpass. Continue to a substantial building or designated shelter when it is safe. On foot, stay on pedestrian routes and away from traffic.
- Enter and follow directions. Once inside, follow staff or emergency-management instructions. Do not leave just because the rain or wind seems to ease.
- Wait for the all-clear. Follow local instructions for the specific hazard. For lightning, use the 30-minute rule described below.
Illustrative decision scenarios
A commuter hears thunder while walking near a highway. The overpass is close, but it is not a designated shelter and reaching it would require entering a roadside area. The safer plan is to use a safe pedestrian route to a substantial enclosed building. If there is no safe route, follow local emergency guidance and do not step into traffic.
A driver sees heavy rain and slowing traffic near an underpass. The low point may collect water, and stopping would create a traffic risk. The driver should not pull beneath the bridge or onto the shoulder. They should follow road and emergency instructions and continue toward a safe enclosed location when conditions allow.
A storm warning arrives at an outdoor event. Staff direct visitors to a designated shelter. Follow their route rather than choosing an overpass based on appearance. If the marked route is blocked or the facility is full, ask staff for the next approved option.
These examples show how to apply the same rule under different conditions: use a designated shelter, not an improvised refuge. They are decision scenarios, not reports of specific incidents.
Verification: Follow the Official All-Clear
An all-clear is an official notice or instruction that says it is safe to leave shelter or resume an activity. A lull in thunder, rain, or wind does not by itself mean the danger has passed. Check alerts and follow instructions from local emergency officials or shelter staff before leaving.
For lightning, the National Weather Service advises waiting at least 30 minutes after the last thunder before resuming outdoor activity. If thunder is heard again, the waiting period starts over. This threshold applies to lightning safety; it is not a general all-clear for tornadoes, flooding, or other storm hazards.
For other hazards, use the local all-clear. Officials may keep a shelter open because roads are flooded, debris is present, or another warning remains in effect. Before leaving, check the route and do not walk or drive through floodwater, closed roads, or areas that responders have restricted.
A useful exit check is simple:
- Is the relevant warning lifted, or have officials given an all-clear?
- Is the route open and safe for your mode of travel?
- Is water, debris, or traffic still a hazard?
- Have shelter staff given any instructions about when and how to leave?
If any answer is unclear, stay in the approved shelter and ask staff or check official updates. Taking a little more time is safer than relying on how the sky looks.
Key Takeaways
A highway overpass is not a public storm shelter unless the responsible authority has formally designated it for that use. Its apparent strength does not establish its ability to protect people, and nearby traffic, wind, debris, and water can create added danger.
Plan around the hazard, not the nearest roof. Know the designated shelter, use a safe route, and follow local directions. For lightning, wait at least 30 minutes after the last thunder before going back outdoors. For all other threats, follow the official all-clear.
Frequently Asked Questions
Is it safe to shelter under a highway overpass during a storm?
No. Do not use an overpass as an improvised shelter. It can expose you to traffic, wind-driven debris, or rising water, and it is not necessarily built or designated to protect people.
Should I stop beneath an overpass during a tornado warning?
No. Do not stop or park beneath an overpass or on a highway shoulder. Follow official guidance and move to a designated storm shelter or suitable building when it is safe.
What should I do if lightning starts while I am driving?
Head toward a substantial enclosed building or remain in a hard-topped vehicle, as conditions allow. Do not stop beneath an overpass or on the shoulder. Follow local alerts and road directions.
How long should I wait after the last thunder?
Wait at least 30 minutes after the last thunder before resuming outdoor activity, following National Weather Service guidance. If you hear thunder again, restart the wait.
Does a concrete overpass count as a storm shelter?
Not by appearance alone. A structure must be assessed and formally designated for the relevant hazard. FEMA P-361 and ICC 500 concern safe-room and storm-shelter design; they do not certify ordinary overpasses.
Can I shelter in an open-sided structure during lightning?
No. Use a substantial enclosed building or a hard-topped vehicle. An open-sided shelter does not provide the same protection from lightning.
Are highway underpasses safe during flooding?
They may collect water and can become dangerous quickly. Keep away from low areas with rising water, and do not walk or drive through floodwater.
Does the MUTCD allow people to use a highway shoulder as shelter?
No. The MUTCD addresses traffic-control devices and work zones. It does not authorize people to use a highway shoulder, bridge, or underpass as storm refuge.
How can I tell whether a shelter is officially designated and open?
Check with local emergency management, venue staff, or another responsible authority. Ask whether it is intended for the current hazard, open now, and reachable by a safe route.
When may I leave a storm shelter?
Follow the official all-clear and shelter staff instructions. For lightning, wait at least 30 minutes after the last thunder; for other hazards, use local guidance.
(This article was written by one of our staff writers, Steven Langford. Visit our Meet the Team page.)
