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The Clear Zone Program promotes public safety, addressing one of the most significant risk factors for fatalities on county roadways. The program identifies and removes objects next to roadways that vehicles leaving the roadway might otherwise hit, creating clear zones. These zones create space for a driver to stop safely or regain control of a vehicle that has left the road, increasing the possibility of a safe recovery and reducing the instances and severity of crashes.

Each year, roadway departure crashes account for more than half of the fatalities. Vehicles leave the roadway for a number of reasons: to avoid collisions with another vehicle, due to mechanical issues like a blown tire, or because of weather issues like ice or fog. Driver fatigue, inattention, speeding, and driving under the influence may lead to roadway departures. Providing a recovery area is important to minimize the risk when vehicles leave the road.

The clear zone and roadside obstacles

King County Clear Zone Program - graphic showing clear zone area.

Roadside obstacles are defined as non-yielding or non-breakaway objects that are more than six inches high, such as trees, boulders, stumps, mailboxes, fences, and utility poles. One study revealed that about 90% of the accidents occurred within ten feet of the pavement edge, so most current road design standards call for constructing roadways with an area clear of objects for a minimum of 10 feet from the outside painted lane edge line on roads without curbing. These modern design standards were not in place for older roads. Additionally, conditions on roadsides change over time as vegetation grows or where adjacent property owners inappropriately place landscaping, fencing or other objects in the road right-of-way.

Break-away mailboxes in the clear zone

Mailboxes are one of the most common fixed obstructions in the right-of-way. Mailboxes are allowed in the clear zone only if they are “break-away” mailboxes. That means wood posts must be no larger than 4"x4" and hollow steel pipe posts must be no larger than 2" in diameter. Specialized breakaway posts may minimize risk of damage and injury. The United States Postal Service guidelines for installing new mailboxes can be found on their website. Concrete, brick or stone pillars or columns are not acceptable on county roads, and present a serious hazard to motorists.

Trees and other vegetation in the clear zone

While we value trees for their beauty and environmental benefits, they are the most commonly struck objects in serious roadside crashes. Planting trees or other vegetation inside the right-of-way is not allowed. Property owners may be liable for accidents involving objects, including trees and shrubs, placed in the right-of-way.

Maintaining a safe road system is the highest priority for King County Road Services. One important way to keep the traveled way safe includes trimming or removing vegetation, shrubs and trees that limit sight distance, and obstruct the ability to see traffic signs and signals and oncoming traffic.

Falling trees along a county road are an extreme hazard to the traveling public. Please contact the Road Helpline at 206-477-8100 or toll-free 1-800-527-6237 to report dangerous trees or limbs. These phones are staffed 24 hours a day, 7 days a week. For non-urgent issues, you can email

On occasion, it may be necessary for county crews to enter private property to remove a tree or limb that poses a danger to the traveling public. Before doing so, the crews will attempt to notify the landowner whenever feasible, unless there is an imminent public safety concern.

Identifying and removing trees and other roadside objects in the clear zone minimizes the consequences of vehicles leaving the road, reducing the number of fatalities and serious injuries.

Implementing the Clear Zone Program

King County has had dedicated run-off-the-road programs for many years. The county reviewed collision data and removed obstacles and/or installed guardrail primarily in locations with collision histories. This last year, the county surveyed all the miles of the highest speed and traffic roadways in the unincorporated areas to create a more comprehensive list of clear zone issues.

With this data, the county is creating a priority array of projects to mitigate identified hazards. A series of factors will be weighed and locations will be prioritized. Factors like prior crash history, speeds, and traffic volumes will allow the county to create a prioritized list of mitigation projects based on likely risk. Depending upon available resources, the county will address some of the highest priority projects each year.

The county is also implementing a public outreach plan to communicate with property owners, community groups, cities, utility companies and others throughout the county about the Clear Zone Program. The goal is to raise awareness about the need to keep roadsides clear of objects to reduce fatalities and injuries for motorists, and about the standards for maintaining the clear zone.

As areas are identified where adjacent property owners have made improvements or where there are trees or other objects in the right-of-way, the county will contact the property owners directly well in advance of any clearing activity. This will give property owners adequate time to remove personal property and get any questions or concerns addressed before any clearing activity occurs.

County right-of-way

If you undertake any activity in the county right-of-way, remember that a permit is required. Find more information about permits.

Contact us

For more information about the Clear Zone Program contact:

Tristan Cook, Community Relations Planner

Call us:

206-477-8100 or 1-800-527-6237 (1-800-KC-ROADS)


Send us an email.