The drivers cannot be not simply ignoring the signs.
The sign is telling them that later down the road they will absolutely get in to problems, and get literally stuck. No one would continue with that certainty of getting stuck or in trouble. On top of that, it cant be repeat offenders either. Some one who has been there before must have gotten caught out, one way or another. Its not like drivers on small roads who see a 6ft width restriction sign, but know through local knowledge that really you can squeeze 7ft wide car through the lane.
What we have is drivers who do not know the road, and in their minds don't think the big huge warning signs are meant for them. In their heads they think it for a another driver on the road in close proximity, even if there is no sign of one.
The problem with road signs is making it known to specific individuals that the message is absolutely for them. The brilliant last resort sign absolutely makes it clear who the message is for.
So the key is to some how make driver know that the message is actually for them specifically.
I have always felt that this is an issue, as i have personally had many problems when interpreting road signage.
For example, i once pissed off some builders by following a truck into their work zone (they were working on a highway lane). The truck had a huge sign on the back that said 'do not follow into work zone', but how can i possibly know if i'm following a truck into a work zone without some indication of where the work zone is? There were no other signs or lights or orange barrels or anything.
Another example is the way exit ramp signage is written where i live. Highway signs don't include units of measure when they refer to distance, so the first few times i saw the sign 'ABC ROAD — 2' i had no idea that it was telling me that the exit for Abc Road was in 2 MILES, not that i was meant to take Exit 2, which happened to be the very next exit after the sign.
The 11foot8 Web site linked elsewhere in the thread mentions that the rail bridge has a flashing sign that says 'OVERHEIGHT WHEN FLASHING'. The site calls this 'pretty good' signage. It makes sense sitting at my computer reading about it, but i can almost guarantee that if i was seeing that sign for the first time on the road i would have absolutely no fucking idea what it was talking about until after i had already crashed into the bridge.
In the US, there's a system called PrePass[1]. It's intention is to be used to allow a truck to bypass weigh-ins. The in-vehicle transponder has a red and green light on it. It could be repurposed to flash red when the vehicle triggers a too-tall warning, though this would be of minimal benefit since it's a small flashing red light most likely in the driver's peripheral vision.
However, I'm unsure if there's any similar system in place in Australia (or most other countries, for that matter.)
I think truck drivers are more or less trained to ignore everything but the last-resort sign. Near where I live, there's a small bridge (railroad on top, road crosses below) with not enough height. It has some limit on vehicle height that is posted on the streets quite some distance away, so that drivers can choose an alternative route. Of course the bridges always will be higher than the posted limit, taking account inaccuracies of the actual vehicle height and movement during driving, so drivers take a certain amount of leeway for granted.
Now I've seen them back out after having touched the posted bar in front of the bridge and having (almost or actually) touched the structure countless times.
Probably with the consecutively more noticable signs in the video, it's made such that the later signs trigger just at slightly bigger heights than the earlier ones, to avoid scaring drivers that made it through the earlier ones un-warned. So I can see that a driver would try testing the later ones, just because he's pretty sure that he might fit, eventually.
The sign is telling them that later down the road they will absolutely get in to problems, and get literally stuck. No one would continue with that certainty of getting stuck or in trouble. On top of that, it cant be repeat offenders either. Some one who has been there before must have gotten caught out, one way or another. Its not like drivers on small roads who see a 6ft width restriction sign, but know through local knowledge that really you can squeeze 7ft wide car through the lane.
What we have is drivers who do not know the road, and in their minds don't think the big huge warning signs are meant for them. In their heads they think it for a another driver on the road in close proximity, even if there is no sign of one.
The problem with road signs is making it known to specific individuals that the message is absolutely for them. The brilliant last resort sign absolutely makes it clear who the message is for.
So the key is to some how make driver know that the message is actually for them specifically.