The First Hill Streetcar lost power Wednesday morning on Broadway with an operator and two passengers on board helpless to stop it before coming to a fortunate stop at Yesler. There were no collisions or injuries in an incident that has prompted officials to keep the service closed until more can be learned about why car 405 — the gold streetcar — failed.

The early hour of the 6:07 AM incident and good fortune left the roadway clear of obstacles for a streetcar route that shares lanes with vehicular traffic.

Andrew Glass Hastings, the Seattle Department of Transportation’s director of transit and mobility, called the failure “an electromechanical malfunction” and said inspectors have isolated the problem to a circuit breaker-like load contactor that shut down the vehicle’s power to its operational system.

That set off a chain of events that engaged the system’s parking brake, leaving the trolley’s operator unable to control the vehicle. The trolley traveled downhill some two and a half blocks, Glass Hastings said, at its “operational speed of 20 MPH” before coming to a stop on E Yesler in front of the community center where passengers were offloaded and the vehicle was towed back to the system’s service facility at 7th and Charles in the International District.

“The operator did what he was supposed to, the vehicle operated as it was designed,” Glass Hastings said. “Unfortunately, without power, the parking brake locked the wheels, and, at that speed, on that grade, the vehicle slid two and a half blocks.”

The decision to inspect the entire fleet of seven Czech-designed streetcars — six serve the First Hill line while the 7th plies the streets of South Lake Union — and shut down the service came about eight hours later, Glass Hastings said, “out of abundance of caution.”

While the cars are being inspected, the First Hill Streetcar line will remain out of service with Metro operating shuttles serving a portion of the route’s stops.

The First Hill Streetcar began service in January in 2016 after months of delay. The start of service on the line was bogged down, in part, by longer-than-expected testing on the propulsion system designed specifically for the First Hill line. The system uses regenerative braking during downhill sections in order to power special batteries allowing streetcars to periodically detach from their overhead wires so they can travel alongside city busses. The system was developed for the First Hill Streetcar to reduce overhead wire conflicts with the Metro trolley buses. In 2015, CHS reported more details of some of the issues that caused the rollout of the service to be delayed including “water-damaged inverters.”

In 2014, Czech manufacturer Inekon incurred a backlog of orders and a short supply of parts, including brakes, holding up production of the Seattle streetcars.

The Seattle Department of Transportation says that around 3,000 riders utilize the First Hill Streetcar daily.