Big-rig route planning: how to route a large RV safely

The single most important idea in big-rig route planning is this: your GPS thinks you drive a car. A Class A motorhome can run 12 to 13 feet tall and weigh 15 tons or more, but standard navigation apps optimize for the fastest car route — they don't know your height, your weight, your length, or that you're carrying propane. That's how RVers end up nose-to-nose with an 11-foot underpass. Planning a safe route means giving the map the information the car apps never ask for.

Step 1: Know your rig's real numbers

Everything downstream depends on four measurements. Get them right once and write them down.

• Height. Measure from the ground to your single highest point — usually the roof air conditioner, sometimes an antenna or vent. Manufacturers frequently quote height without the A/C, so trust your own tape measure, not the brochure. Most RVs land at or under 13 feet 6 inches, the practical ceiling many older bridges and tunnels were built to.
• Weight. Use your loaded weight (with water, gear, and passengers), not the dry weight on the spec sheet. Heavy motorhomes and fifth wheels can exceed posted tonnage limits on older rural bridges.
• Length. Your total length — including anything you tow — drives turn radius, campsite fit, and some road and park restrictions.
• Width and propane. Note your width (mirrors matter on narrow roads) and whether you carry propane, which matters at some tunnels.

A useful habit: assume posted clearances are optimistic. Repaving can shave an inch or two off the real number, and you never want to be counting on the last inch of margin.

Step 2: Understand the four hazards car GPS ignores

Low clearances (the famous one)

The most-watched low bridge in America is the "can-opener" — the Norfolk Southern–Gregson Street overpass in Durham, North Carolina. For decades it cleared just 11 feet 8 inches, peeling the roofs off box trucks caught on camera. In October 2019 it was raised eight inches to 12 feet 4 inches — and vehicles still hit it. The lesson isn't about one bridge; it's that posted-clearance data alone won't save you. You need routing that actively steers around structures your rig can't clear.

Weight-limited bridges

Plenty of secondary roads and older bridges carry posted tonnage limits. A loaded Class A well over 30,000 pounds has no business on a bridge rated for less, and a car app will route you across it without a second thought. Weight-aware routing uses your actual loaded weight to keep you off structures you'd overload.

Propane and tunnel restrictions

Many tunnels restrict liquid propane (LP gas): some prohibit it outright, others require the tank valve to be closed and turned off. Major tunnels around Baltimore, Boston, New York City, and the Hampton Roads area all carry propane rules of one kind or another. Because these rules vary by facility and do change, always confirm current signage and the operating authority's guidance for any tunnel on your route. RV Compass flags each propane-restricted tunnel on your route as a propane caution and says it out loud before you reach it. Details in our propane and tunnels guide.

Steep grades and tight roads

Elevation is the hazard people underestimate. A route that's fine on paper can hide an 8,000-foot pass with a white-knuckle descent. Knowing the climbs in advance turns a mountain crossing into a plan instead of a surprise. In RV Compass, pick a drive in the elevation panel to see its own profile with every steep grade listed (where it starts, how steep, how long, how far it drops), and in navigation the app calls out steep downgrades a mile before they start. Our mountain grades guide covers how to drive them.

Step 3: Let a routing engine do the filtering

Here's how RV-safe routing actually works. You build a vehicle profile — height, width, length, weight, and axle count, and feed it to a routing engine that penalizes or excludes road segments carrying restrictive attributes: low clearances, weight limits, RV/truck bans, and tight turns. The clearance and restriction data comes from state and local DOT databases, field surveys, and RVer reports, and good engines record the lowest posted value to stay safe.

This is a solved problem in commercial routing. Open-source engines like Valhalla — the same engine Tesla uses for in-car navigation — include a truck costing model that applies a vehicle's dimensions at query time. RV Compass runs on Valhalla, self-hosted and tuned for rigs, so height, weight, and length are first-class inputs on every route rather than an afterthought. One tuning choice matters for big rigs: the truck costing is set to favor staying on the interstate, so rig routes don't hop off onto ramps and frontage roads to save a few seconds. Propane rigs are not routed as hazmat trucks; they get a warning before restricted tunnels instead.

A quick big-rig route-planning checklist

1. Measure and record your height (with A/C), loaded weight, length, and width.
2. Set whether you carry propane.
3. Plan the route with a tool that applies those numbers — not a car app.
4. Scan the route for low clearances, weight-limited bridges, and propane-restricted tunnels (RV Compass lists each one in the route report).
5. Check each drive's elevation profile for passes and steep grades.
6. Confirm your overnight stops fit a big rig (length and pull-through).
7. Verify any tunnel or bridge restriction against current official signage before you rely on it.
8. Plan fuel stops around your real range. Diesel pushers and tow rigs burn through a tank fast (see planning fuel stops for a big rig).
9. Keep GPX or a backup device handy for the cab.

Or let RV Compass do it automatically

Every step above is what RV Compass is built to do from one rig profile you set once: the dimension-aware routing, a clearance check on every leg, propane cautions before restricted tunnels, steep grades for each drive, fuel range with truck stops, big-rig campground filters, and honest ETAs that explain each detour. If you'd rather not audit every bridge by hand, that's the whole point.

Map data can't tell you how a road rides, so RVers flag the rough stretches from the cab with rough road reports. Drivers heading the same way get a warning before they reach one, and you can plan a trip around them.

Next: see how RV Compass stacks up in our comparison with RV LIFE Trip Wizard, or why it's a fair RV Trip Wizard alternative for big rigs.