Designing Bus Routes and Schedules
This article is the fifth 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 V: Blocking, Run Cutting and Rostering
Now that we have our schedule we are ready to do the final step in the design of bus routes and schedules: "cut" our schedule up into pieces that actual drivers will drive. But before we do there is one thing we have to do to our schedule - block the trips. A vehicle block is a set of trips that one particular bus does in the course of a day. We start with the first trip and connect it with (usually) the next trip that leaves the end of the line after it arrives. When there are no more trips to connect to the bus returns to the garage. We repeat the process until every trip is in a block. Fun fact about blocks: sometimes a bus has a sign in the lower front windshield by the door - this sign displays what block the bus is doing and is used by supervisors to make sure service is operating smoothly.
Blocking is a much tougher process if the bus route operates very frequently than if the route operates infrequently. Often the capacity of the terminus point will be an issue and blocking must be managed in such a way that a limited number of buses will be expected to be simultaneously laying over at the terminus. Also, if a bus routes operates out of more than one garage or division creative blocking can be used to ensure that the block both starts and ends at the same location; assuming the block would operate out of the closest garage to that starting and ending location doing this will save deadhead time and money. The blocking of routes that operate infrequently is often very straightforward, but if too much or too little layover results than the route may have to be interlined with another that shares a common terminus and headway.
Now that are blocking is done, we will assign the blocks to different drivers to drive. A driver's daily work assignment is often known as a duty, and a duty may be made up of one piece - if the driver has a straight run, reporting for work, working eight hours, and then going home - or more than one piece if the driver has a split run. A block may have one piece - if it is eight hours or less and one driver does the whole thing - or it may have multiple pieces. The process of breaking up the blocks into individual pieces and duties is called run cutting. Before the advent of computers, transit system schedulers literally put pieces of paper representing the blocks up on the wall or on the floor and used scissors to cut them into pieces. Nowadays software makes it much easier to perform this once very tedious step.
Run cutting is made vastly more complicated if it has to conform with a large number of rules restricting the kind of duties that can be made. For example, many union contracts call for a minimum percentage of straight runs, limit the number of part time duties, and prevent split runs from starting before or ending after a certain time.
Once the run cutting is completed, different transit systems have different procedures for how drivers pick runs. Virtually all transit systems operate what are known as bids: certain times of the year, usually two or three, when drivers come into the garage and, in seniority order, state what duties they are going to work for the next few months. However, there are two different ways in which drivers can select duties.
In one way, called cafeteria-style bidding, drivers pick individual duties for each day type that they are working and specify what days off they would like. For example, if a driver wanted Tuesday and Wednesday off in cafeteria-style bidding they would pick one run to work Monday, Thursday, and Friday; one run to work on Saturday; one run to work on Sunday; and, if applicable, a run to work on any holidays. Certain systems allow drivers to pick a different run each weekday instead of one weekday run.
In contrast are the systems that use what is known as rostering. In rostering, the scheduler, usually with the aid of the computer, assembles duties into weekly packages. When the driver comes into bid, instead of specifying what days off they would like and what they would like to do weekdays, Saturday, and Sunday they instead specify what roster position they would like.
Effective blocking and run cutting are extremely important to the agency's bottom line. Ineffective blocking will result in excessive amounts of layover and deadheading. Ineffective run cutting will result in either too much overtime or too much guarantee time (many union contracts state that drivers will be paid for a minimum of eight hours of work - if the duty they are driving is only seven and one half hours long then they will get paid for eight: the extra thirty minutes is known as guarantee time). Although planners often get more recognition, it is the schedulers who can often make the difference between financial stability and financial catastrophe for the transit agency.
This series of five articles has given you a broad overview of the kind of thoughts and activities that go into the creation of a bus route and schedule. I hope it has given you a newfound appreciation for the complexities of service planning.