Washington State Trailer Towing Rules

By Lynne Haley Rose - Updated June 06, 2017
Trailer hitch ball and bar and plastic top

Trailer towing laws in Washington state are determined and enforced by the Washington State Patrol. Be sure to brush up on regulations regarding weight, dimensions, and licensing for your trailer prior to hitting the roads of the Evergreen state. Add a measure of common sense regarding your vehicle's load capacity, and pack your load wisely, and you can avoid time-consuming delays in transit.

Size Limits

The maximum length allowed for a trailer in Washington state is 53 feet. If you obtain a special permit, you can pull a unit up to 56 feet. A truck and trailer rig can measure no more than 75 feet. The maximum allowable width for a trailer is 8 feet, 6 inches, and the load must be under 14 feet high. These limits are designed to make travel safe on average road widths and freeway overpass heights.

Weight Limits

If you are pulling your trailer with a vehicle that has a single-axle setup, such as a light-duty pickup or SUV, the WSP sets a weight limit on your load of 20,000 pounds. For a dual-axle rig, regulations allow you to pull up to 34,000 pounds. Your rig's tires also figure in to the weight restrictions, so if you are near the load limit, consider that WSP law states you can carry up to 600 pounds per inch width of tire.

Trailer Hitch Regulations

For a Class 1 trailer–less than 1 ton maximum gross weight–you must use a hitch ball at least 1 7/8 inches in diameter rated to withstand 3 tons of longitudinal–lengthwise–tension and 1.5 tons of vertical tension. For a Class 2 trailer–1 to 1.75 tons in weight–your hitch ball should be a minimum of 2 inches in diameter and rated for 5.5 tons of longitudinal tension and 2.5 tons of vertical tension. Class 3 trailers–between 1.75 tons and 2.5 tons–requires a 2-inch minimum ball and a rating to haul 7.5 tons longitudinal tension and 3.5 tons vertical tension.

Safety Chains and Attachment Rules

Safety chains that extend from the neck of the trailer to the trailer hitch on your vehicle must comply with Washington state regulations. Each safety chain must be rated for 2 tons when you are pulling a Class 1 trailer; 1.75 tons for a Class 2 trailer; 2.5 tons for a Class 3 trailer; and the maximum gross trailer weight for a Class 4 trailer. The attaching mechanisms–hooks and eyes–must meet similar load specifications.

Rules of Thumb for Towing

No matter where your are towing a trailer, whether it is in Washington state or elsewhere, you should keep in mind some rules that will help you avoid trouble down the road. Remember to adjust your driving when you are pulling a trailer. Corner more slowly to ensure that your trailer does not create a traffic hazard. In addition, slow down your driving in general if you wish to avoid damage to your load.

About the Author

I have an MFA degree in Creative Writing and am a published poet who has received several poetry awards. I have established a reputation as an environmental activist, both through the group I co-founded -- see alternativeone.org -- and through a series of op-ed pieces in Montana newspapers. I have written extensively on alternative energy, recycling and endangered species.

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