The objective of installing a longitudinal barrier is to contain and redirect errant vehicles so that they do not cross medians into the path of other vehicles, or impact roadside features. Most barrier systems have been designed and tested to account for passenger vehicles and not motorcyclists. A recent study showed that motorcyclists accounted for 40% of all fatalities resulting from a guard fence collision compared to 60% for occupants of all other vehicle types. (Gabier et al., 2022) Motorcyclists are clearly overrepresented in impacts given they comprise only 3% of the registered vehicles.

Motorcyclists are vulnerable to injury when they strike longitudinal barriers. Motorcyclists separated from their motorcycles can slide beneath a guard fence beam because the gap beneath the beam can allow a motorcyclist to impact the unprotected posts. When a seated motorcyclist impacts a guard fence and is ejected, they can slide across the guard fence and impact the top of the posts and beam edge. Concrete barriers on the outside edge of elevated structures present fall risk to the ejected motorcyclists.

Treatment

: Designers need to apply good road safety practice to manage roadside risks for all road users. The first consideration should be if the roadside feature that requires longitudinal barriers can be removed or avoided entirely.

Where a barrier is identified as required for a new design, and where there are specific risks to motorcyclists, it is important that the type of barrier chosen minimizes the risk to these road users. Specific barrier treatments have been developed and tested (Schulz et al., 2023 and Dobrovolny et al., 2018) to help mitigate risks to motorcyclists. A properly designed rubrail Table of Contents Instructions Reference Links 20-7 | Roadway Design Manual| 2024 element beneath a guard fence beam can reduce the potential for interaction of a sliding motorcyclist with a post. A cap rail mounted on top of the guard fence can mitigate risk of an ejected motorcyclists interacting with the top of the posts or beam edge. Refer to for a crash tested rubrail and caprail system. A containment fence mounted behind a concrete barrier can help capture an ejected motorcyclist to prevent a fall off an elevated structure.

has additional guidance with respect to Roadside Safety hardware applications that can mitigate risks to motorcyclists.

The provision of an add on feature to a vehicle barrier is a risk-based approach usually evidenced through collision data or where other mitigation measures cannot be introduced. A recent evaluation of Texas motorcycle fixed object crashes shows a high risk when motorcyclists impact bridges and guard fences on curved roadways (Schulz et al., 2023). High risk is also indicated for motorcyclists impacting concrete barriers in high-speed locations (≥50 mi/h) and AADT ≥928.

Such ‘add on’ products need to be compatible with the restraint system to which it is being attached.