A pedestrian leaning off a Muni median in downtown San Francisco was struck by a bus Thursday evening, snarling traffic for hours.

The incident occurred around 7:45 p.m. when a 31-Balboa heading inbound toward the Ferry Plaza went into the left lane while traveling east on Market Street at New Montgomery.

According to Muni spokesman Paul Rose, the pedestrian had their back to the bus when they were struck and suffered a head injury. The pedestrian is said to be in stable condition.

The stops for the 31 are typically in the right lane of Market Street. Whether the bus crossed the median where the F-Market, 6-Parnassus, 71-Haight and N-Judah Owl bus pick up and drop off passengers, is still under investigation, Rose said.

A guardrail on the median at New Montgomery was visibly bent and a second guardrail was missing completely. A pool of blood was located in front of the bent guardrail.

"I don't know if [the bus] did" smash the guardrail, Rose said.

The driver of the bus has been placed on nondriving status and will be tested for drugs or alcohol, which is normal Muni protocol, Rose said.

The driver remained at the scene and was visibly shaken.

The bus remained at the scene for more than two hours. Historic streetcars were taken out of service because the bus involved in the crash was stopped on the rails used by the F-line. Traffic was backed up to  Fourth Street affecting the commute on many streets trying to feed on to Market, including Geary.

akoskey@sfexaminer.com