CDL: Appropriate Space Above, Below, and During Turns

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Managing Space: To the Sides, Overhead, Below, and Through Turns

Large vehicles need more room than cars do — not just in front, but on every side, above, below, and especially while turning. This article covers how to manage the space around your vehicle beyond what's directly ahead: keeping clear of the vehicles beside you, protecting the roof and undercarriage, executing turns without hitting anything, and finding a safe gap to cross or enter traffic.

Space to the Sides

Commercial vehicles are often wide enough to take up nearly an entire lane, which leaves very little margin for error. Safe drivers make the most of the limited space they have by keeping the vehicle centered in the lane and avoiding unnecessary time spent driving alongside other vehicles.

Stay Centered in Your Lane

Keeping your vehicle centered helps preserve safe clearance on both sides. If your vehicle is on the wider side, that clearance margin shrinks even further, making centering all the more important.

Avoid Traveling Alongside Other Vehicles

Driving next to other traffic for extended periods carries two specific risks: another driver could suddenly change lanes into you, or you could find yourself boxed in right when you need to change lanes yourself. Whenever possible, look for an open stretch of road away from other traffic. In heavy traffic, an open spot may be hard to find — in that case, try to keep as much distance as you can from nearby vehicles, and either drop back or move ahead so the other driver has a clear view of your vehicle.

Watch for Strong Winds

Strong crosswinds can make it difficult to hold your lane, and this problem tends to be worse for lighter vehicles. Wind gusts can be especially severe coming out of tunnels. Avoid driving alongside other vehicles in these conditions whenever you can.

Space Overhead

Striking an overhead object is a real danger for tall commercial vehicles, so maintaining adequate clearance above your vehicle is essential.

• Don't assume posted bridge or overpass heights are accurate — repaving or packed snow can reduce the actual clearance below what's listed.
• Cargo weight affects a van's height — an empty van rides higher than a loaded one. Just because you cleared a bridge while loaded doesn't guarantee you'll clear it when empty.
• If you're unsure whether you have enough room to pass under something, slow down, and if you're still not confident, take a different route. Low bridges and underpasses often have warning signs, but not always.
• Certain roads can cause a vehicle to lean, creating clearance problems near the edge of the road with objects like signs, trees, or bridge supports. In these situations, it can help to drive a bit closer to the center of the road.
• Before backing into an area, get out and check overhead for hazards like trees, branches, or electrical wires — these are easy to miss while focused on backing, so check for other hazards at the same time.

Space Below

It's easy to overlook the space underneath a vehicle, but that clearance can shrink significantly when the vehicle is heavily loaded. This is a common concern on dirt roads and unpaved lots. Drainage channels crossing a road can cause the ends of a vehicle to drag, so cross these depressions carefully to avoid getting hung up.

Railroad tracks present a similar risk, particularly for trailers with low underneath clearance. As with drainage channels, don't risk getting stuck halfway across a crossing.

Space for Turns

Because large vehicles turn wide and experience off-tracking — where the rear wheels follow a tighter path than the front wheels — they can strike other vehicles or objects during a turn if space isn't managed carefully.

Right Turns

• Turn slowly, which gives both you and other drivers more time to react to potential problems.
• If your vehicle can't complete a right turn without swinging into another lane, turn wide as you finish the turn while keeping the rear of the vehicle close to the curb. This discourages other drivers from trying to pass you on the right.
• Don't swing wide to the left when beginning a right turn. A driver behind you may assume you're turning left and attempt to pass on the right, potentially resulting in a collision as you complete your turn.
• If you need to cross into the oncoming lane to complete a turn, watch carefully for oncoming vehicles and give them room to pass or stop. Don't back up to make room for them, since doing so could mean hitting someone behind you.

Left Turns

Before starting a left turn, make sure you've reached the center of the intersection first. Turning too early risks having the left side of your vehicle strike another vehicle because of off-tracking.

When an intersection has two left-turn lanes, always choose the outside lane rather than the inside one. Starting in the inside lane may force you to swing wide during the turn, which means having to watch for vehicles alongside you in the lane to your right — a spot where visibility is limited. Drivers positioned to your left, by contrast, are much easier to see.

Space Needed to Cross or Enter Traffic

The size and weight of a commercial vehicle change what's required to safely cross or merge into traffic. Keep these points in mind:

• Because large vehicles accelerate more slowly and need more room to maneuver, you'll typically need a bigger gap in traffic to enter safely than you would in a car.
• Acceleration performance changes with the load — a heavier load means you should allow extra room before pulling out.
• Before starting across a road, confirm that you can make it all the way across before oncoming traffic arrives.

Managing space isn't only about what's directly in front of your vehicle. Staying aware of the room beside, above, below, and around your vehicle — especially through turns and when entering traffic — is what allows a large commercial vehicle to move through traffic and tight spaces without incident.