It’s a cautionary tale told in hushed tones at RV parks and campgrounds around the country – the ubiquitous yarn of the motorhome that lost its air conditioners, satellite dish, or even it entire roof to an overhead span. Some overpasses even have websites, like the 11 foot 8 inch “Can Opener Bridge” in North Carolina; truckers and RVers alike have fallen victim to it.

Several readers wrote me while I was in New England, asking with trepidation about the notoriously low vertical clearances there. I must admit, I was nervous about it as I planned the trip. Many overpasses, especially train trestles, were erected in the East over 100 years ago, before there were national standards on height clearances. Here’s a good example in Massachusetts:

Nellie and I survived four months in New England, and here are my tips and tricks on how to avoid low clearances in big rigs. After all, vertical obstacles exist everywhere, not just on the highway, and not just in the East.

1. Measure Your Rig, Pad The Number, And Memorize It. I hired a driver safety instructor to teach me how to drive Nellie. We spent three hours together. The very first thing he did was climb to the top of the rig and drop a tape to me on the ground to measure height. (He advised against relying on manufacturers’ measurements, especially on used rigs which may have aftermarket modifications.) We measured from the highest point – the front air conditioner cover – and the total was 12’8”. Adding in wiggle room for tire pressure, potholes and speed bumps, we agreed I should avoid any heights under 13‘5“. That number is seared in my brain. For a while I even had a Post-it note on the dashboard. Sometime later, when I replaced the rear air conditioner, I measured again from the new cover to confirm nothing had changed.

2. Be Vigilant. When I first started driving Nellie, I made a sign for the dashboard: “Look Up.” We’re not just talking bridges and train trestles here. Low hanging branches, gas station carports (which often have their heights posted on them), and power lines are now your sworn enemies.

For vertical clearances, be vigilant for posted warning signs. I have seen signs posted as far back as 10 miles, and as close as on the obstruction itself (more on that in a minute).

Keep an eye out for big trucks. There is nothing more serendipitous and reassuring than seeing a big rig pass you in the other direction as you approach a bridge or overpass about which you are uncertain!

3. The Rig Is For Traveling; The Toad Is For Exploring. Now obviously, I am speaking here to people who drive large motorhomes and have secondary means of transportation. When you are moving locations to a campground or RV park, there is obviously a non-obstructed way to get there, or all those other rigs wouldn’t already be there! Park the rig at your temporary home, then take the motorcycle or bicycle or toad or rental car to see the sights. Almost every time I have gotten off the beaten path while driving the rig, it has been a mistake, from dirt and gravel roads to low hanging branches to no turn-arounds. Speaking of “off the beaten path,” I once read a very good piece of advice on an RV forum: “Don’t drive your rig down roads without stripes.”

Here is the entrance to a waterfront park in a little town in Maine; I was glad I drove there in Toad and not Nellie.

4. Review The Upcoming Park’s Website. RV parks are usually pretty good at posting any quirky directions or travel issues on their websites. For example, they may advise not to use the posted address in a GPS and may suggest a different address. The “about“ or “FAQ” sections may list additional routes for getting to the park if there are height or weight issues.

5. Invest In An RV GPS, And Always Use It. I have a Garmin RV GPS, which records the rig’s height and weight and is supposed to warn me about any upcoming obstructions. I say “supposed to“ because Lola, my GPS, is developmentally disabled. She is quite the scofflaw, always encouraging me to take toll lanes, even when there is no cash option and I have not enrolled in electronic monitoring in the particular area. In El Paso, she directed me to drive over earthen irrigation bridges, which I refused to do in a 30,000 pound vehicle towing a 3,500 pound car. She has proclaimed, “You have arrived!” when we were not at the destination. Driving the barren desert back roads between Palm Springs and Las Vegas, having seen no other vehicles for over an hour, she proclaimed, “There is currently light traffic on your route!”

Suffice it to say, I do not rely exclusively on Lola. I have redundancies, which are discussed below. But recently, my faith in Lola was somewhat restored. As I was researching a place for an overnight stay near Niagara Falls, an online forum warned of a 12‘5“ overpass on the route to a casino. Holding a printed alternative route in my hand, I waited to see if Lola would correctly predict the upcoming obstruction, and she did.

Even when you have a map, or printed driving instructions, or you think you know where you’re going, plot your course in the RV GPS. Here’s why:

When I’m driving the rig and encounter a sign declaring a vertical obstacle less than a mile away, it makes more than my lips pucker. A quick glance at the RV GPS will tell me the distance to my next turn, and I can swiftly and efficiently determine if the obstacle will be in my path.

6. Build In Route Redundancies. Review state DOT websites. Get a Truckers’ Atlas, which lists restricted routes and low clearances. Use your phone as a secondary GPS, but don’t rely on it exclusively, especially if you are not using a trucking app. Install a trucking app.

7. If You Get Stuck, Don’t Panic. I swear, sometimes an overpass’s height is not forewarned, then you see it posted on the structure itself, with no nearby exits or places to turn around. I am knocking on wood really hard right now, because this has yet to happen to me where my rig was too tall. But, I have already thought about what I would do if I encountered a vertical obstacle and could not turn around. It would be a good idea for you to do the same.

If you are driving by yourself, you simply have no choice but to call local law enforcement. They can divert traffic and block lanes so that you can turn around and even drive the wrong way if you have to. Do not attempt to do this on your own!

If there is more than one person in the rig, you can attempt to divert traffic and turn around, but it is a good idea to have triangles and cones and flares on board for this, and the other person can direct both you and traffic from outside. That person should be wearing a safety vest.

Another option is to attempt to pass under the obstacle. Did you know that in some states, any vertical obstruction under 14 feet tall is automatically posted a foot less? For example, an underpass with an actual clearance of 13’9” may be posted as 12’9″.

I have several caveats. Not every state follows this rule, so what you’re facing may be exactly the height as posted. Never attempt this alone. You will need a person directing you from outside the rig. Preferably, that person will be local law enforcement, who will know exactly how tall the obstruction is.

Arriving in Texas after four months in New England, I laughed and shook my head at the sign declaring the height of the upcoming overpass: 19 feet. It’s true what they say about things being bigger in Texas. I breathed a sigh of relief.