I recently wrote about the Big Blue Bus’s updated stroller policy for the City of Santa Monica’s blog. The policy is actually very progressive. Not only do you not have to fold your child’s stroller once on board, you can ask the operator to deploy the bus’s wheelchair ramp for you.
Santa Monica is now only one of three operators in the County of Los Angeles (out of almost two dozen) that do not require you to fold the stroller once on board. The other two are Los Angeles Metro and the Glendale Beeline.
By the way, the Glendale Beeline (nine fixed routes) actually has a dedicated page on their website which spells out how to ride transit with a stroller and I had no trouble locating this from navigating their website, which is excellent.