Crashing into low bridges

Trucks crash into low bridges regularly. So this brings up a question, how do you design to stop them?

 · 2 min read
 · Andy McKay

In British Columbia, trucks have been crashing into bridges regularly. The BC Trucking Association commented recently on this as there have been 17 bridge strikes along BC Highways. Although I haven't found any measure of the costs:

In July 2022, the province spent around $1 million to fix a collision on 192 Street


So that begs the question, how would you design it so that a truck doesn't crash into bridge. What measures would you take? Signage? Detection? Currently it sounds like they working on considering higher fines, stepper penalties and long suspensions.

But let's take a look at one of the most famous bridges in North America, "the can opener" or "11 foot 8". It's 11 foot 8 high, or 3.556 meters high and it's in the city of Durham, North Carolina. Raising the bridge would mean huge changes to the train tracks above it. Lowering the road would mean huge changes to the sewer system underneath it. You can watch videos of this bridge and the trucks crashing into it on the website.

The city of Durham has installed “low clearance” signs on each of the 3 blocks leading up to the trestle... The signage is good, and the vast majority of truck drivers notice the problem and avoid the bridge. Large signs alert driver to the low clearance several blocks before the bridge. Half a block before the trestle, a sensor detects overheight vehicles and triggers an LED blackout warning sign that was installed in May 2016. That same sensor also triggers a red-light phase at the traffic light directly in front of the trestle (installed in March 2016), so the driver has 50 seconds to read the warning sign next to the red traffic light and consider their next move.


Just to highlight that: the driver has 50 seconds to read the warning sign next to the red traffic light and then drive forward and crash into it. You can see all these things in this still:

Yes, that's also the truck blowing through a red light.

What struck me with all this, is what measures do you actually have to take to stop people doing something like this? Admittedly the design of the roads and intersections make this one a truly hard one to fix. The nearby side streets make it hard to put a warning barrier further up the road, and perhaps people turning left or right might not see the signs. But I'm sure limiting access to the side streets has been discussed.

Bringing this back to British Columbia, or any other jurisdiction, what would be enough to stop people going under low bridges? How many warning signs do you need? How many flashing lights and overhead sensors? How many red lights?

Since the bridge was slightly raised in 2019, by 8 inches it sounds like things have improved from before, but its still happening, more often now with rental trucks.