multiple buses can fit one stop

[kianzarrin]

• if the segment is large(like the image above), multiple buses can fit at the bus stop at once and serve passengers.
• furthermore if the next bus is close, current bus can stop a bit more further ahead (like the image above) to make space for the next bus. this happens in the real world too.
• this works smoothly if the bus follows the black path in the image above (#1688)