Rumble strips and bicyclists: What works, what is safe | Adventure Cycling Association

Headlines are quick hits from media outlets from Missouri and around the world. Follow the headline link for the full story. The source of this headline says:

Rumble strips are a proven method for decreasing roadway departure crashes for motorized vehicles; however, when not installed properly, they can be a serious danger to cyclists’ safety. Rumble strips can force cyclists into the travel lane with high speed traffic when installed on roads with little or no shoulder or down the middle of the existing shoulder.

We work to ensure that all road users––both motorists and cyclists––can safely enjoy America’s roads. We advocate for transportation agencies to enact rumble strip policies that provide a minimum of four feet of usable shoulder for cyclists and ensure the quality control of rumble strip installation.

**Rumble Strip Best Practices
Based on Federal Highway Administration (FHWA) standards and the studies/reports noted below, these are the rumble strip best practices recommendations that provide the minimum standards to safely accommodate bicyclists:

* Shoulder width: No rumble strips or stripes installed on shoulders less than four feet wide.

* Placement: Adjacent to or on the white line, providing a minimum of four feet of usable shoulder to the right of the rumble strip.

* Frequency: 10-foot gaps allow cyclists to navigate away from the shoulder if needed.

* Depth: 0.375 inches

* Width: 5 inches

* Length: 6 inches 

* Center line rumble strips: Ensure a minimum four foot shoulder width when installing center line rumble strips. AASHTO recommends six-foot minimum shoulder width when both center line and shoulder rumble strips are present.

MoBikeFed comment: We would like to see MoDOT adopt more of these national standards for rumble strips, particularly allowing regular gaps in rumble strips and requiring a minimum of 4 feet shoulder space to the right of any rumble strips.

Though MoDOT's standards for rumble strips could use some improvement, some of MoDOT's innovations in rumble strip design, made at the urging of MoBikeFed and Missouri bicycle advocates in the 2000s, have become standard national recommendations today.

Primarily, the idea to put narrow rumble strips directly under the white line (the "fog line")--a design known as "rumple stripes"--was first pioneered in Missouri.

The advantage of this design is that it leaves all remaining shoulder space for bicycle use--while also giving motorists the earliest possible warning that they are diverging from the travel lane.

Previous to this, it was common to put very wide rumble strips directly in the middle of the shoulder--meaning that even 4-8 foot shoulders could be completely ruined for bicycling.