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Overpass Crash?! How Tall Is Your RV?

Overpass Crash?! How Tall Is Your RV?

Have you ever been driving your RV, come to an overpass, weren’t sure of the clearance, slowed down… then drove under it anyway? If so, you certainly know, in hindsight, that slowing down doesn’t make your RV shorter.

When I used to transform bus driver trainees into professional motorcoach operators, there were lots of overpasses in the major metropolitan area where I worked. Some of them were quite low, with only inches to spare taking an MCI under them. And some had only one advance warning sign, with no clearance listed on the overpass itself.

Once students were pretty well along in their training, and getting close to being on their own, I would sometimes challenge their observational and decision-making skills by having them drive down one of those streets with a very low bridge. The moment we passed the clearance sign, and I knew the bridge itself wasn’t marked, I would immediately ask them if that bridge up ahead was high enough for us to fit. There were always several trainees in each class, and I’d sometimes see a knowing smile or two from others, as they waited for the response from the student who was behind the wheel.

The best trainees would respond with something like “The clearance sign showed 11′ 6″ and we’re 11′ even (the height of an MC-9), so we should be good.” I would always know when a trainee wasn’t quite ready to pilot a situation like this solo, when their first reaction to my question was silence, and the lifting of their right foot off the accelerator.

I knew that they had either not seen the clearance sign, didn’t know the height of the bus, or both. The only thing left to observe was their decision making skills, now under pressure.

I’d ask again “Are you sure we can fit?” or “Should we make a turn to avoid it?” as we slowly continued to approach the overpass.

The most unsure would continue to slow down as they decided what to do. These were already mostly-trained about-to-be-professionals, and I’d remind them that they’re the driver, and it’s their decision how to proceed.

Some would say they weren’t sure, even as we continued to roll toward the overpass. And trust me, a 6-inch clearance above an MC-9 looks from inside like you’re going to hit it for sure. Inevitably, some trainees would continue forward, even after clearly stating they had no idea if we’d make it.

That behavior would elicit a lesson from me that I have zero doubt every trainee aboard carries with them to this day. As we came even with the bridge, I would bang my clipboard against the inside wall of the bus. Besides providing an unforgettable lesson that you NEVER drive under an overpass that you think you might hit, it probably also served as a secondary test of everyone’s heart, on top of the echocardiogram that everyone had already passed as part of their CDL physical exam.

Needless to say, I’ve probably made more than my fair share of drivers practically jump out of their skin this way. But I’m confident that not one of the trainees who was driving, or riding, on board with me during one of those clipboard-banging episodes has ever driven under an overpass without being 110% certain they’d fit.

During my time in the bus business, one of our company’s drivers sheered the roof off the top of an MCI like a can-opener, at speed, with a load of passengers on board (no, that driver was not one of my students). Low overpasses are no joke.

In the video, we provide only the briefest mention of RV GPS units and truck driver atlases. There’s a reason for that. First, RV-specific GPS models and other electronic aids (such as smartphone apps) aren’t 100% dependable, and we’ve read of dissatisfaction of the other features that those models offer. And the Motor Carriers’ Road Atlas is all well and good. But RVers aren’t truckers. Many of us are most interested in exploring more remote scenic byways, as opposed to truckers, who generally prefer interstates and other major roads for getting their job done in the most timely and efficient manner.

And most of all, obstacle avoidance isn’t something I like to outsource. There is no better method for avoiding an overpass than knowing your rig’s height and paying attention as you drive.


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Thanks to 11foot8.com for graciously providing permission for us to use their footage. Copyright Jürgen Henn – 11foot8.com. Check out their YouTube channel here.

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mark hoffmann

Tuesday 13th of February 2018

Great videos guys . . . We have an '04 Essex, so it is the same vintage as yours, and when I went topside to measure height, I found that the roof was not parallel to the ground. Our tallest point was the rear AC cover even though it was not the tallest fixture on the roof. As I remember it was a couple of inches different from the front of the coach to the back, but could be more dependent on the coach. In any case, I think you covered it by adding the margin for error... .

TheRVgeeks

Tuesday 13th of February 2018

Hi Mark! Thanks for the additional info. It was the '04/'05-era Essex that made us first fall in love with Newmar! We couldn't even afford the mortgage, but luckily, the Mountain Aire was a close second for us, and we've been happy with ours for nearly 13 years now (still with that more-affordable mortgage though). LOL You might be interested in the first part of our Live Q&A follow-up to this video. Just after the 5 minute, 30 second mark, we go into considerable detail about measuring the height of an RV with a roof that isn't flat (either side-to-side or front-to-rear). You might find some of that discussion interesting. You can find it here. Safe travels - Peter & John

Curt Johnson

Sunday 28th of January 2018

I noticed going up I 95 on the east coast that many bridges aren’t marked for clearance. Is there a minimum height before they are required to post a clearance? Also, is there a variance in the standard policy of reporting, or not reporting clearance between US highways, State roads or County roads?

TheRVgeeks

Sunday 28th of January 2018

Hi Curt! According to the DOT, anything under 14' is considered under height: https://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_verticalclearance.cfm The reason there are so many overpasses with no markings on major highways, especially interstates, is because they're 14' or higher.

Doug LaFeve

Wednesday 17th of January 2018

My only comment would be that it might be best to measure, as you said on a level surface and with the motor running until your air system reaches it's max pressure. Then shut down and measure immediately. Your tires should be pressurized for your weight and load distribution prior to measuring. Another question though - if you are running empty i.e. not at full load capacity will you air system give you a higher ride? On a big RV you could be losing a lot of weight if running a low fuel tank and no water, that could be 1600 to 1900 lbs or more depending upon the size of your respective tanks. Thank you for all the highly informative videos, as a newbie with a 43Ft Class A DP I have learned a lot from your YouTube and website.

TheRVgeeks

Wednesday 17th of January 2018

Hi Doug! Thanks for the great comments and questions. I happen to have considerable experience with a wide range of air-bag equipped vehicles, from 1950s, 60s and 70s-era GM transit buses, to 1980s and 90s-era MCIs, to 2000s-era diesel pusher motorhomes. The only ones that have any issue with losing air system pressure and coming down off the air bags are the really old ones, which can end up with deflated air bags in a matter of hours, and certainly overnight. That's the result of slow leaks developing in older air systems over time. Anything even reasonably new will have such a tightly sealed air system that it's just not an issue. When we shut down our nearly-13-year-old motorhome for the night in a Wal-Mart lot for example (leaving the RV up on air bags, since we wouldn't level in that situation), there is almost no airing up required the next morning. It stays virtually all the way up on the air bags, with almost no loss of air pressure on the gauges, even with us moving around inside. Modern air systems are very tight. That said, if you want to be overly careful about it, just run your RV until it airs up all the way, and then do your measuring in a reasonable amount of time after shutting it down... maybe within an hour. You won't have any height difference than if you were idling the engine, so that's not needed. As far as the rig being empty or fully loaded, one of the things about air suspension is that it is far more robust than spring-type systems, which is why it's used in heavy-duty vehicles like buses. A great example of how an air-suspended chassis are oblivious to load is a charter bus. I routinely took an empty bus to pick up a full load of 50 passenger and all of their luggage. Figuring 175 lbs for an adult and one large suitcase, that's an instant 8,750 lb addition to the vehicle. The height of the bus stayed precisely the same. For a gas rig or travel trailer, empty weight might be slightly higher than fully loaded. But that's exactly why we always leave several inches of extra space overhead, for exactly that sort of variance. As far as tire pressure goes, they should always be set correctly anyway, so of course do that first. We wouldn't worry too much about an inch or two up or down. Just don't cut things so close that it matters.

Rodney

Wednesday 17th of January 2018

Loved the video as this has been one of my concerns for years. Fortunately I have a 6' level and could measure from the highest point to the ground. I have a 2001 Dutch Star and it measured 12'-2", so I use 12'-6" for the height. However, I've always wondered how much the air-assist ride would raise the motor home up when driving. I should have measured when the engine was running but didn't think about it then nor now when parking. Do you have a estimate of the distance? I liked your suggestion of using 13' as a safety factor when traveling.

I was curious about what you taught your students to do when they come upon an overpass they thought might be too low. Stop and have someone observe as they slowly drove under? If unable to pass under try to turn around (on a two line rode that might be impossible). I'm sure you have a suggestion or two to handle this situation.

TheRVgeeks

Wednesday 17th of January 2018

Hey Rodney! Great questions. We'd estimate that our air bags drop the RV about 4-6" although we've never measured that. You don't actually have to worry about whether or not you measure with the engine running. As long as the rig has not been parked overnight since you shut the engine down, it will still be fully up on the air bags. They just don't drop that fast. If you want to be sure, measure within an hour of shutting down.

As far as coming upon a low overpass... as a tour & charter bus operator, there were many times when I'd be traveling in areas I'd never been to before. And many of those tours were to areas away from Interstate highways, depending on where the tour group was going. And remember, this was back in the 80s and 90s, before the internet or GPS existed. So us drivers would be flying completely solo, with nothing more than state maps, and our wits to keep us safe.

The most important thing to do (of course already knowing that the bus was 11' tall) was to pay attention. Most low overpasses have some sort of advance warning in time to change course or turn around. I found that the general rule was if a country road lead to a 10' 6" overpass, there would be a warning sign no further along than the last intersection where I could turn to avoid it. Being vigilant for those types of signs (as well as low weight limits, but that's a topic for another video), is the single most important key element for avoiding being stuck on a remote road with no way under a bridge, and a potentially very difficult, dangerous, or impossible u-turn required.

If I were ever to come upon a low bridge (marked or not) that I wasn't sure I could fit under, with no way to turn around or back up, I'd stop dead at the side of the road with hazard lights flashing, get out and walk down the road to sight back under the bridge to see if I could tell how close it was (you often can if you walk far enough ahead). If it still seemed very close, and I had someone with me, I'd prefer have them walk out ahead, and watch as I crawled under, signaling to me as needed. This would be easier with an RV than a bus, because the idea of stopping on the side of the road like that with passengers on board isn't the kind of thing that inspires confidence among them! And add to that the liability of asking one of them to walk out ahead on the road to spot for me. Not fun.

But I will tell you what is even less fun than any of that... hitting the bridge. I always used to tell students: If you think you're going to hit something, and you keep going anyway because you're worried about blocking traffic, being embarrassed in front of passengers, or any other reason, imagine how embarrassed you'll be when the crash happens. I'd tell them that anything else that happens will be forgotten within a few weeks, except a collision. That will stay with you for life. No matter what you have to do, don't hit that bridge! Stay cool, deal with the situation, and learn from it. You can even use a close call as a great story someday (crashes never seem to be worthy of laughing, even in hindsight). I have a few of those stories is myself, but this is too long already. ;-) Hope this helps.

aelkins1

Wednesday 17th of January 2018

My hubby has been watching (and showing me) videos from 11foot8 for years. Those -- and other YouTube videos about various crashes -- have made me more alert even when just driving my little car. It's infotainment! lol

TheRVgeeks

Wednesday 17th of January 2018

We've always loved that channel, too! So we were really pleased that they readily gave us permission to use some of their footage. :)

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