The cart is empty

Cannot find your purchased courses? Click here to Login!

The maximum height of a vehicle in North America is 13' 6" (4.15m).

Overhead Clearances | Bus, Truck & RV Drivers



Overhead clearances must be understood at a glance by bus, truck & RV drivers. 

Something that people driving larger vehicles are prone to striking and in a recent camping trip there was a building, as you can see in the photo here of a building and the corner of it had been struck by somebody with an RV trailer obviously.

The building kinda sat at an odd angle but the the soffit overhung the roadway and if people were not careful and didn't see the obstruction, they were going to run into it.

So one of the key points of overhead obstructions is that stay away from trees and buildings: they like to take bites out of vehicles.

And just give you two examples in the time that I was driving commercial vehicles I had to altercations - both minor.

But still struck overhead obstructions.

One of them was a at a loading dock in Florida.

The dock itself was kind of inside the building and there was a roll-up door.

Well, when I went back to open the doors at the back the trailer, I didn't realize that somebody had pushed the door all the way up.

And it was down about a foot, so when I'm back in obviously struck the overhead door and the shipper wrote on my bills of lading that I had struck the door that it was my responsibility.

So I as the driver had been held responsible for the door being struck.

A height sign for larger vehicle and is too low in most places.<p>Only in New York might you be able to go under this low obstruction.

Another incident: I was hauling garbage and the the garbage was very dry, and on the transfer trucks that came out of Toronto they loaded the trucks to maximum weight capacity which was about 35 tonnes.

You pulled on the scale and the trailer wasn't loaded, they backed you back in and they proceeded to with large excavator hammer on as much garbage as they could to get you to maximum weight.

What I didn't notice when I pulled the tarp over the load was that it was sticking up five or six inches.

I went under an underpass in Michigan that was exactly thirteen feet 6 inches probably like two or three inches of clearance.

It pulled the entire tarp off the back of the trailer and some of the garbage blew off because it was couple miles down the road to the garbage dump.

It's gonna happen!

Maximum Height of Your Vehicle

If you're driving professionally you're going to get into trouble and hopefully it's a minor incident not a major incident.

Professional drivers need to know their vehicles or 4.15 meters or thirteen feet six inches in the States.

Read the road signs.

If you're on minor roads are in suburban areas and there's an overpass, make sure that you know exactly what the height of your vehicle is.

For recreational drivers and Uhaul drivers Uhaul is very good about labeling inside the vehicle what the exact height of the vehicle is.

RV Drivers - Yes, you're driving a large vehicle too

Recreational drivers, on the other hand, do not know what the height of their vehicle is and it's imperative that you take the time and measure it.

Most of the time for recreational drivers, you're going to get into trouble in gas stations, refilling station.

The canopies - nine times out of ten they're going to be enough clearance because in the last couple of decades these have all been renovated and raised up because the people with larger RV trailers getting in there.

Again the story I opened with - be careful in campsites.

Don't Work the Day for Free:: DOT Weigh Scale Checklist

This checklist will provide you with a list of paperwork that you need to bring into the authorities when you get pulled into the scale house.

• DID YOU KNOW? :: Bus & truck drivers are the only drivers that have their own police force (DOT, CVSE, MTO, etc.);

• SMART :: There's a lot of paperwork you must produce for authorities at the weigh scale;

• SELF-CONFIDENCE :: Bring all paperwork in one hit & impress the diesel bears!

Because in most cases, it's you that gets the fine...NOT the company!

Get Your Driver's Test Checklist Now!

GPS Units - most are designed for cars

Never trust a GPS (Global Positioning Satellite) unit even if it's a commercial unit.

Use your eyes.

As Malcolm Reynolds says in the movie "Serenity":

"you wanna find somebody, use your eyes."

It's the same thing if you are unclear that you're gonna fit under a bridge, overpass, or other clearance and you don't know for sure because you don't know the height of your vehicle or you don't know the height up the overhead clearance.

Get out of your vehicle and look.

And don't look standing next to the vehicle.

You have to get back away from the vehicle a good distance to get a perspective of how high your vehicle is and how high the obstruction is.

If the obstruction is down here you were definitely not gonna go under.

Finally, if you find yourself in that situation where you have stopped, and traffic is backed up behind you and you can't get around, you can't get the vehicle turned around because there's not enough room you're gonna have to back up.

Often times people are very helpful.

If you put your 4-ways on, back up slowly, they'll move out of the way, they'll accommodate you.

Somebody with local knowledge will help you.

They're very good about that, people love helping truck drivers.

New York State

One time in New York state, there was a bridge overpass my introduction to New York that measures from the center of the hub, as opposed to from the road surface.

All the signs are labeled 12' 6", 12' 8" 13 feet.

Well your vehicles is 13' 6", it's not gonna fit under there.

I stopped at this bridge where I was given directions It said 12' 8".

I'm not gonna fit under there.

One of the locals came up and told me the trucks went under there all the time.

It was very helpful.

Of course I went very slowly under the bridge and of course I fit.

The thing about New York State is that they still haven't rectified this problem of measuring from the center of the hub.

So know that New York State is somewhat different.

But again do not trust your GPS, do not trust the signs.

If you're unsure stop, get out and look.

And in dire cases where you can't get backed up and traffic will not help you out, call the police.

That's what they're for: come out, stop traffic, move traffic around, and get backed up.

Have a Plan to Get Around a Low Clearance

You try and do a U-turn, as in the video that I'm showing you here.

Sometimes you can do more damage to your vehicle than if you just wait and think about what you're gonna do logically.

OK, overhead obstructions and clearances: know the height of your vehicle 13 feet six inches 13 feet six inches in the US; 4.15 meters in Canada.

Recreational vehicles: measure your vehicle.

Know how high it is! Be careful at gas station canopies.

Uhaul drivers, it's inside the truck; it's very well labeled how high that vehicle is.

Do not bash the front of the vehicle in.

Commercial drivers, recreational drivers, Uhaul rental vehicles.

You know! Stop and look.

Get out and look if you're the least bit unsure.

And do not proceed - backup.

Call the police.

Have an action plan in place that will see you safe and other road users safe as well.

Log in to comment
Default Image

Applied Stroke - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day as part of his/her pre-trip inspection. In some jurisdications, drivers must use the applied stroke method; in others, they…
Default Image

Pry Bar - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day. In many jurisdications, drivers are allowed to use the pry bar method; in others , they must use the applied stroke…
Default Image

Compressor or Build-up Test (Air Brakes)

Author: Rick
Depending on which province you're in, the air buildup time or compressor test has somewhat different paramenters. Still, all require that the diesel motor be at a fast idle. A fast idle on a diesel engine is between 900 &1200 rpm.
air brake adjustment

Air Brake Manual Adjustment – Pry Bar Method

Author: Rick
Using the pry bar method, confirm that the brake is in fact out of adjustment. After confirming that the brake is out-of-adjustment and it is equipped with a manual slack adjuster, complete the following steps to bring the brake back into adjustment. If one…
The one-way check valve is primary responsible for the division of the air brake system into a primary and secondary sub-system.

One-Way Check Valves

Author: Rick
A cattle chute with one-way gates allows the cows to only move in one direction – forward. A one-way check valve in an air brake system works exactly the same – it allows air to only move in one direction – forward through the system. The one-way check valves…
Default Image

Air Brake Chambers

Author: Rick
Convert air pressure into a strong mechanical force to apply the foundation brakes.
Default Image

Air Gauge(s)

Author: Rick
The gauges are in either pounds per square inch (psi) or Kilopascals (kPa). These measure the amount of air pressure in the primary and secondary air tanks.
Default Image

Automatic Front Wheel Limiting Valve

Author: Rick
To reduce application pressure to the steering axle brakes during most braking situations. Reduced pressure to the steer axle brakes occurs for most braking applications. Only during hard braking is there equivalent pressure delivered to both the front and…
A bobtail proportioning valve will move most of the braking to the front steer axles when there's not trailer attached.

Bobtail Proportioning Valve

Author: Rick
A bobtail proportioning valve great increases braking safety owing to different weight distribution.
Brake fade is the only reason that a modern air brake system will fail.

Brake Fade

Author: Rick
Brake faide is the only reason that a modern air brake system will fail.
Default Image

Brake Linings & Drums

Author: Rick
To stop the vehicle, brake linings rub against the brake drum. This action creates friction, converting the vehicle's forward energy of motion into heat energy, which stops the vehicle’s tires. If the tires have traction, the vehicle will come to a stop. The…
A caging bolt is used to release the emergency brakes in the event of an emergency (life or death situation).

Caging Bolt

Author: Rick
Allows the spring brakes to be manually released in an emergency - a dire emergency.
Default Image

Compounding Air Brakes

Author: Rick
OBSOLETE Making a heavy service brake application while the parking brakes are applied. This is often an error of truck driving school students.
Air Brakes Simply Explained is a comprehensive manual that guarantees that you will pass your air brake ticket first time.

Brake Pedal - Foot Valve OR Treadle Valve

Author: Rick
MUST KNOW The brake pedal applies the service brakes - truck, or truck and trailer brakes. In other words, the brake pedal brings the vehicle to a stop when it it depressed. SHOULD KNOW The foot valve operates the secondary and primary sub systems…
You must know what a manual front wheel limiting valve is for your CDL air brake test. These are no longer found on modern trucks.

Manual Front Wheel Limiting Valve

Author: Rick
OBSOLETE To reduce application pressure to the steering axle by 50 % compared to the drive axle brakes, when required by reduced road conditions (rain, snow or ice). The system consists of a dash switch with 2 positions: Dry Road: 100% front wheel braking; in…
After a brake application, air is exhausted from the air brake system via the quick release valve to reduce brake lag.

Quick Release Valve

Author: Rick
The quick release valve moves to reduce brake lag in the air brake system.
Default Image

Relay Emergency Valve

Author: Rick
OBSOLETE Fills the trailer air tanks (reservoir) and applies and releases the trailer service brakes. The relay emergency valve also applies the trailer emergency brakes in the event of a trailer breakaway or normal disconnect. Knowledge Test Question: In the…
The relay valve takes a message from the brake pedal and draws air directly from the air tank to the brake chamber, thus reducing brake lag.

Relay Valve

Author: Rick
Several relay valve throughout the air brake system reduce brake lag, thus allowing the brakes to apply faster.
Default Image

Air Tanks (Reservoirs)

Author: Rick
Stores compressed air for braking and for other air operated accessories. The air tanks are the first fail-safe in the air brake system. In the unlikely event that the air compressor fell of the side of the engine, the air tanks (reservoirs) store enough air…
Default Image

Slack Adjuster

Author: Rick
Slack adjusters have three purposes: 1) To convert the forward linear motion of the push rod into rotary motion of the camshaft. The slack adjuster works on exactly the same principle as a box end wrench on a nut. 2) To act as a lever, thus generating greater…
Default Image

Spring Brake Modulator (Inversion) Valve

Author: Rick
OBSOLETE Used on some vehicles with dual air systems. This device provides a means of using the force of the spring brakes to assist in stopping a vehicle in an event of a failure in the rear (primary) air system.
Default Image

Spring Parking Brake (Emergency)

Author: Rick
Applies the parking brakes of the air brake equipped vehicle indefinitely – if needed of course. The parking brakes are held in the “ON” position by the mechanical force of the springs; these spring parking brakes are held in the “OFF” position by system air…
Default Image

Stop Light Switch

Author: Rick
Activates the brake lights when a service brake application is made by the driver.
On most trucks, the air lines to the trailer are plumbed into the tractor protection valve.

Tractor Protection Valve

Author: Rick
The tractor protection valve protect the tractors air supply from being depleted in the event of a trailer breakaway.
Default Image

Trailer Hand Control (Spike)

Author: Rick
OBSOLETE Independently applies and releases the trailer service brakes. Knowledge Test Question: This air brake control is not to be used for parking. Although most tractors are still equipped with hand valves, beyond a trailer service tug test, these air…
Default Image

Two-way Check Valves

Author: Rick
Must be used whenever two sources of air are used to operate a single device or system. For CDL air brake test, the driver must know there are 2 in the system.
Before unhooking a semi-trailer, ensure that the ground will support the weight of the landing gear.

Unhooking Semi-Trailer

Author: Rick
Before unhooking a semi-trailer, ensure that the ground will support the weight of the landing gear. MUST KNOW LAP 1) Landing Gear down 2) Air Lines & Electrical (Disconnect) 3) Pin (Pulled & Unlocked)
Always, always check the jaws are closed around the king pin to ensure that the trailer is in fact hooked to the truck.

Hooking a Semi-Trailer

Author: Rick
Always check with a flashlight that the 5th Wheel jaws are locked around the king pin.
blog image

Brake Fade | Air Brakes

Author: Rick
Although air brakes are more-or-less buletproof these, like all braking systems, have one failing: BRAKE FADE.

© Smart Drive Test Inc. 2024.

Contact Us: [email protected]