how to write circular for all employees maintain the Bus timings

Our suppose to leave at 5 pm, but due to some employees every day we are getting late
though they have genuine work related issues but it is very inconvenient to other employees and we don't have any other transport facility so we have to wait till they finish their work
please guide me how to write a circular for all employees to adhere the timelines but want to handle it little bit softly

Strictly mention in circular that Bus timing is 5pm and you have to reach before 15 min at the bus,If anyone is late then bus will move at exact time which is 5pm.

Hi
If the bus is being operated by the employer, there is no way you can put a circular and ask all of the employees to leave their work and join for journey back home. You are contradicting yourself when you say that there is no transport facility and some of the employees take their time to finish the work and report late for the return journey.
So long as the employees are not idling at work you may not be able to put any circular officially.
Thanks and Regards