I think it can be a case by case thing by street. M street for example in Georgetown, the buses for the most part just go East/West down the street.

So making each crosswalk on the streets in between elevated makes sense to me and leaving the main M st alone.

Removing a lane and adding a seperate emergency / transit access lane seperate by bollards or a curb that isn't elevated as well is an option.

But also doesn't slow them down by much, few seconds at most https://oth.opengov.com/production/uploads/portals/49/forum/issue/7970/issue_asset/asset/9705/Traffic_Calming_Fact_Sheets.pdf