The three groups of people most at risk during a tornado are those who are outdoors, those in mobile/manufactured homes, or those on the road in vehicles. The first two locations are detailed in other sections of this safety guide. How to handle severe weather situations on the road is detailed below.
Vehicles - cars, trucks, sport utility vehicles, RVs, 18-wheelers, boats, trains, planes, etc. - are terrible places to be when a severe thunderstorm threatens. Fortunately, these situations can be avoided most of the time by being ALERT to the possibility of severe storms and tornadoes.
All types of vehicles can be blown over, rolled, crushed, lifted or otherwise destroyed by even a weak tornado. People have been hurt or killed when large trees crushed their cars. Below are some safety tips.
Every situation is different, and if faced with a tornado threat while on the road, your best course of action will depend on your exact location, the tornado's location, speed, and direction of movement, road options available to you, nearby structures, time of day, traffic, weather conditions you're experiencing.
If the tornado is far enough away and road options and traffic allow, you should try to find a substantial building for shelter. Follow the basic tornado safety guidelines (get in - get down - cover up). Motorists have found truck stops, convenience stores, restaurants and other businesses to be adequate shelters in a tornado situation. Walk-in coolers can sometimes make a good shelter.
While you should never try to outrun a tornado in your vehicle, you may, in some situations, be able to get out of the tornado's way by driving out of its path, or simply stopping and allowing the tornado to pass. Again, this can be extremely dangerous unless traffic, time of day and road options allow you to see the tornado, determine which way it's moving (and how fast), find a road option that will take you out of its path (while avoiding other storms) and to safe shelter.
The worst-case scenario for motorists would be to be trapped in your vehicle on the road with no escape possible. This scenario could occur in more densely populated areas, in metropolitan areas at rush-hour or in high traffic situations, or on limited access roadways, such as interstates or turnpikes, where it might not be possible to quickly exit and find safe shelter. It is in these situations when it may become necessary to leave your vehicle and seek shelter in a ditch, culvert or low spot.
Highway overpasses are NOT tornado shelters, and these should be avoided. The reasons, which are numerous, have been listed and explained in a presentation from WFO Norman, OK.
Ditches, culverts, and ravines should be used only as an absolute last resort. You will be exposed to flying debris, rain and hail, lightning and extreme wind. People have survived by seeking shelter in ditches, but people have also died. If you must leave your vehicle to seek shelter in a ditch, you should try to get as far away from the vehicle, as well as any other potential "missiles" as possible.