In North American English, bus bulb refers to an arrangement by which a sidewalk is extended outwards for a bus stop; typically the bus bulb replaces roadway that would otherwise be part of a parking lane. With bus bulbs, a bus can stay in its traffic lane to discharge and pick up passengers, instead of having to pull over to the curb. This prevents buses from being delayed by having to pull back into traffic; however, that comes at the expense of delaying other vehicles that must wait behind the bus, especially on streets that only provide one traffic lane in each direction.