Some people who rely on public transit in California may have noticed delays in transportation after several bus drivers staged a protest over concerns of safety.

Los Angeles Metro bus drivers staged a "sick-out" on Friday (May 3) over safety concerns following a series of violent attacks on public transit. The action led to delays on several bus lines, including Lines 2, 4, 18, 20, 40, 45, 53, 66, 70, 108, 110, 111, 206 and 720, per ABC 7.

The drivers' protest comes in the wake of several assaults on Metro buses and trains. Last month, a woman was fatally stabbed by a transient while waiting for a Metro train. In another incident, a bus driver was stabbed in the chest by a passenger in Willowbrook. These incidents have raised concerns about the safety of both drivers and passengers, KTLA reports.

In response to the drivers' action, L.A. Metro issued a statement acknowledging the drivers' fears and frustrations.

"Bus operators are the face of Metro to more than 80% of Metro riders. They are the lifeblood of the Metro organization. We understand their and their families' fear in the face of the senseless assaults some have experienced primarily resulting from the twin crises of untreated mental illness and drug addiction," the statement reads in part.

The transit agency said it has expedited the installation of protective barriers on buses and is redeploying safety and security personnel on board buses to deter assaults. However, the agency also urged drivers to reconsider their action, stating that intentionally calling in sick puts customers at risk and violates Metro's Collective Bargaining Agreement.

The drivers' union, SMART, has not yet made a public statement about the sick-out. However, last month, the union demanded changes including armed security officers on buses, felony-level charges for those who assault drivers and transit workers, silent alarms to alert police of live shooters, emergency exits for drivers, and cashless fare payments, according to CBS News.