This weekend, at least seven semi-trailer trucks were blown over on one stretch of I-40 in Decatur and Henderson counties. The road was closed following the incident until the scene could be cleared and re-opened for traffic. There are reports of other incidents of trucks getting blown over the same area. In Humphreys and Benton counties, tractor-trailers traversing the bridge linking the two counties were also overturned. In this post, Stillman and Friedland discusses this hazard and other dangers of large truck traffic. We will also have some tips for securing your RV during storms.
The phenomenon Of Straight-Line Winds
Let’s take a look at the phenomenon of straight-line winds. While the term “straight-line winds” seems less threatening than “tornado”, both present real dangers. In fact, straight-line winds can be just as damaging and forceful as tornado gusts. Both wind threats come from thunderstorm conditions, so it is not surprising that they are similar in intensity. In cases where severe wind damage occurs, weather experts can tell the difference between the two types of wind damage only by the pattern of the damage, not by severity. As you would expect, straight-line winds result in straight patterns of object and debris dispersal, and tornadoes fling things in a swirling path.
A Few Facts About Straight-Line Winds And Their Impact
- Straight-line winds are severe thunderstorm downdrafts that present a clear danger to trucks when wind speeds exceed 53-56 m.p.h.
- The greatest danger is when these winds hit the semi-truck broadside, causing it to flip over.
- Unlike cars, trucks are designed aerodynamically only for forward motion, and they present large flat sides. When hit on the side the result is wind impact and not wind flow.
The danger increases as wind speed increases, and as trucks accelerate. Slower speeds are safer. As one source notes, the stronger the winds the greater the likelihood of most vehicles being tipped over and thrown. Yet, while semi-trucks are blown over at winds above 56 m.p.h., only at 200 m.p.h. can we expect most other vehicles to be tipped over and lifted or thrown. The bottom line here is that while trucks are massively larger and heavier than other vehicles, they are much more susceptible to wind impact.
Three take-home points
- Monitor weather conditions to plan accordingly and avoid driving in stormy weather, especially on interstates with high-volume truck traffic.
- If you find yourself stuck in this situation, steer clear of large trucks, maintaining a safe stopping distance, even if you are in another lane.
- Be extra cautious when crossing bridges; wind exposure is increased on bridges, and your options for avoiding a crash depend on following distance alone.
Note About Recreational Vehicles
Please also note that if you own or are using a recreational vehicle (RV)—especially if it is large and boxy — take precautions when storm conditions are approaching:
- Do not park it under trees
- Remove awnings
- Use stabilizer jacks
- Park near a sheltering wall or hill to minimize the impact
As we have reported in many blog posts, mixed truck and car traffic pose many challenges to all drivers. A wind-like challenge for small-car drivers is the suction created by fast-moving trucks on freeways. Your lightweight vehicle can be sucked into or in front of a fast-moving truck. Again, avoid driving close to trucks, and avoid passing them if you can.
Here are some general pointers to consider, especially are we approach the holiday season and truck traffic increases with goods deliveries. Semi-trailer traffic will only be increasing in the next couple of months, as Christmas approaches.
- Always keeps a safe stopping distance from all vehicle traffic, keeping in mind that stopping distances are longer for larger vehicles
- Remember that trucks, unlike cars have very deep blind spots, especially on the right-hand side. Do not assume that you are visible to the driver; drive accordingly
- Be especially cautious near exits and be alert to trucks making lanes changes
As we the season changes and we encounter stormier weather, it is important to be more alert to changes in road conditions. Expect the unexpected! With November fast approaching, start thinking about winterizing your car, and keep on top of expected weather conditions. To the best of our knowledge, no cars were impacted by the weekend’s truck incidents, and most were blown off the roadway. Yet it is easy to see how one could easily plow head-on into a truck blown into the lane of traffic, especially in bridge traffic.
Stillman and Friedland will continue to update and advise you as we move together toward what we hope will be a joyous holiday season for all.
Because we care…