Cross sections can have signs, lighting columns and other road furniture within them, which if poorly located, can result in injuries if struck by a motorcyclist. Introducing these structures with breakaway supports can provide an important tool in reducing the severity of vehicle related collisions, however the standard for testing the safety of features does not take into account motorcycles or motorcyclists.

As a result, designers need to consider that breakaway supports may not perform in the same manner when hit by a motorcycle or motorcyclist. These supports may not shear or deflect as intended, potentially resulting in higher severity injuries for this group of road users. The use or need for this infrastructure should be carefully considered.

Treatment

: When developing highway schemes that incorporate roadside furniture the positioning of these features needs to be carefully considered.

Designers need to understand and apply good road safety practice to manage roadside risks for all road users.

The principle of remove, relocate, reduce, and protect the roadside feature ensures that the concerns of motorcyclists are included when introducing road equipment support structures into a design.

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.

The presence and condition of shoulders may affect motorcyclist safety. A lack of shoulders offers a motorcyclist no place to take an evasive riding action if necessary. A stalled motorcyclist on a roadway without a shoulder or with only a narrow shoulder is especially vulnerable to moving traffic on the adjacent lane. A wide shoulder provides an errant motorcyclist recovery space before impacting a fixed roadside object. Paving currently unpaved shoulders so they can be used for these purposes is a recommended method of assisting in motorcycle recovery and avoidance maneuvers. Plans should ensure that paved shoulder edges are tapered to the unpaved area and do not present a dropoff.

Shoulder width and AADT are critical factors that influence motorcycle crash frequency. In rural environments, locations with narrow shoulders provide little recovery space for vehicles negotiating a horizontal curve. Rural roadways with shoulder widths of 6-ft or less will have approximately 52 percent greater likelihood of crashes occurring at horizontal curve locations.

Clear zone widths in the , which is the basis for guidance in the RDM, are calculated using a passenger car or truck as the design vehicle. A clear zone for a motorcycle might need to consider a motorcyclist who has been thrown from his or her bike, making it uncertain if the AASHTO clear zone widths are adequate. A wider clear zone is better because it allows a motorcyclist more distance to decelerate before striking a roadside feature.

Motorcycles differ from other vehicles in that they overhang their wheel track by about 1-ft to 2-ft on each side and because they lean to change direction, which markedly alters the Table of Contents Instructions Reference Links Roadway Design Manual | 20-8 clearance they require when travelling upright. Failure to account for these characteristics may result in riders colliding with poles, signs, or fences that are placed too close to the edge of the pavement.

When objects cannot be located outside the clear zone, agencies have recommended a variety of methods to minimize risk to motorcyclists including: