Designing Bus Routes and Schedules
This article is the fourth in a series of articles about how bus routes and schedules get designed, from the initial determination of the route to ongoing maintenance of the schedule. Practices mentioned in the articles are ones that I engage in on a daily basis that I have found to be useful in my twenty-eight years of studying and following transit systems. TCRP Report 100 , put out by the federal government, is essential reading on this subject.
Part IV: Writing the Bus Schedule
Now that we know where our route is going, what our stops are, and how long it will take to travel between our stops we are ready to write the actual bus schedule. Virtually all transit systems with more than fifty vehicles write bus schedules with the assistance of computer software. Currently two computer scheduling software packages dominate the market: Hastus, made by GIRO Corporation of Montreal, Quebec; and Trapeze, made by the Trapeze Corporation of Mississauga, Ontario. Using scheduling software enables the scheduler to easy complete many schedule iterations by hand, and makes the provision of things such as timed transfers much easier to achieve. The most important benefit of scheduling software lies in its run cutting function, which we will look at in Part V of this series.
In order to schedule a particular route we need to know two things: the service span of the route and the frequency/headway of the route. Because this is a new route, we will determine the service span via a policy basis. If our route was already existing, then we would consider a demand based service span based on the ridership of the first and last trips. If nobody was riding the first or last trips then, obviously, we would reduce the service span. On the other hand, if a significant number of people were riding the first or last trips - perhaps 50% more than were riding the second or next to last trips - then we would consider extending the service span.
A policy based service span is usually based on a bus operating through generally accepted industry definitions of specific time periods. For example, the A.M. peak period is generally defined as between 6 AM and 9 AM; mid-day is between 9 AM and 3 PM; the P.M. peak period is between 3 PM and 6 PM; early evening is between 6 PM and 10 PM; and late evening is after 10 PM. Different areas will have slight adjustments to the above categories.
In addition, when we consider the service span we also need to take into account the run cutting process. Having a service span in hours that is a multiple of four will make it easier and more cost effective to schedule the drivers (for example, if our bus route operated from 6 AM to 10 PM it would have a service span of sixteen hours). Achieving this is not always possible.
If our route operates along the same pathways as other routes, then a service span which includes only the peak periods may be acceptable. Otherwise our route should operate at the very least the mid-day period in addition to the peak periods, for a service span of 6 AM - 6 PM. Because the low income riders that make up a large percentage of the total ridership of the average system often work jobs that start or end at odd hours, strong consideration must be given to operate the route through the early evening as well, and also before the A.M. peak period starts. If resources permit then Saturday and Sunday service should be operated as well.