A request for advance payment turned into a physical altercation Saturday, when a taxi driver's stick-wielding fare took umbrage after being asked to pay up.

According to the San Francisco Police Department, the 47-year-old cab driver picked up a man in his mid-20s at 1:30 a.m. Saturday at the intersection of Market and Main Streets in San Francisco.

The early-morning traveler wanted to go to the East Bay, the SFPD reports, and the cabbie asked him "to pay up front."

This apparently upset the passenger, who police say "became upset and began punching" the cab driver "on his face and head."

In an effort to escape his agitated fare, the cab driver "jumped out of his cab." The passenger pursued him, police say, and "jabbed [the driver] multiple times with a stick" before fleeing on foot. He hasn't been seen since.

The driver had non-life-threatening "facial/forehead/back of hands bruising" as a result of the attack, but refused transport to the hospital for treatment.

San Francisco Municipal Transportation Agency regulations state that cab drivers are "authorized to collect 150 percent of the metered rate for any trips originating in the City with a final destination that is more than 15 miles beyond City limits," as well as to "collect bridge tolls in advance from passengers whose destination requires the crossing of a toll bridge, regardless of the direction in which the toll is collected." An SFPD spokesperson did not know the amount of the upfront payment the cab driver was requesting, or why the fare was standing at Market and Main with a weaponized stick at 1:30 in the morning.