Relay was a free, self-driving shuttle provided by Fairfax County between the Dunn Loring Metrorail Station and the Mosaic District in Merrifield. The shuttle's software was programmed to follow a prerecorded path at a maximum speed of 10 miles per hour. It relied on several sensors (localization lasers, GPS, odometry and cameras) to navigate and orient in the environment and follow a predefined network of routes. The sensors and lasers helped detect obstacles in several zones around the vehicle to assist with safe navigation. If vehicles, bicyclists, pedestrians or objects in the road were detected, Relay was programmed to slow or stop to avoid incident.

Although Relay was "autonomous," a Safety Steward always was on board in activate an emergency brake. Fail-safe brakes could be automatically activated to stop the vehicle even when there was no power, or when the vehicle was stationary. In addition, the operator helped ensure safety and accessibility for passengers. Relay was equipped with a ramp to get into the vehicle, as well as restraints for any wheelchair or scooter.

When in operation, FCDOT asked the following of the Relay community:

• Drivers should stay attentive and keep at least 10 feet between their vehicle and Relay; do not use bike lanes or cross double yellow lines to pass the shuttle.
• If a full lane was available, motorists could use that travel lane to legally and safely pass Relay.
• Riders were advised to remain seated with seat belts on in case of emergency stops. Due to the Pandemic, Relay would carry a maximum of six riders.

Fairfax County was responsible for overseeing the shuttle operations. TransDev managed the technology, maintaining the vehicle, providing the safety attendants and providing overall service.

Following a RFP process conducted by Dominion Energy, EasyMile’s EZ10 model was selected for the pilot. At the time of the project, the EZ10 was deployed on public and private roads in more than 25 countries on four continents.

EasyMile’s EZ10 model:

• had more than 200 deployments at the time of selection,
• held up to 12 passengers,
• featured a full set of sensors, including Lidars, cameras, and GPS to ensure safety, and
• featured a built-in, automated electric wheelchair access ramp.

Before going into service, the shuttle underwent extensive testing, received a full safety audit by the state, and was approved by the National Highway Transportation Safety Administration.  

In the event of an emergency, a safety steward always was on the shuttle, and this person was able to shift to a manual operation if necessary.

Relay did not operate in inclement weather, such as heavy rain and snow. Fairfax County Department of Transportation (FCDOT) determined the operating status based on the severity of the weather and shared the shuttle's operating status on this webpage.