Within the earlier unit on service planning, the strategic choices of community and route design, cease structure, and frequency dedication have been described. On this unit, the tactical choices related to making a service schedule (timetabling), making a schedule for automobiles to function the service (car scheduling), and creating work shifts for operators (crew scheduling) are introduced. A sensible guidebook and studying device has been printed just lately.
The motivation for good options to those tactical choices is to attenuate the web working prices to the company. As soon as the timetable is set, the variety of automobiles required to be in income service may also be recognized. When the car schedule is set, the entire mileage and hours for the car fleet are outlined. Lastly, when the crew schedule is set, the entire price of labor (operators) is outlined. Since these elements are the first determinants of working prices, discovering environment friendly options has a direct impact on the underside line.
In lots of instances, these tactical actions are assisted by software program instruments that may generate prime quality options in a brief time period, typically with direct interplay with the planner. In consequence, the scholar might want to seek the advice of different sources to determine and to analyze the precise software program instruments that could be obtainable, akin to these described in a current publication.
The final thought behind timetabling is to create a schedule for service. As inputs, one would think about the frequency of service for the given route (see earlier unit) and the anticipated journey instances between stops on the route. The latter may very well be decided both by historic expertise or by estimates primarily based on site visitors situations, car acceleration and deceleration traits, anticipated dwell instances, and so on.
Let h be the chosen headway for a route, maybe for a particular time interval of the day.
Let tij be the time between cease i and cease j alongside the route, the place i and j are adjoining stops. The journey instances between stops, tij, can fluctuate by time of day, notably as they might be affected by site visitors situations. They could additionally replicate any slack time constructed into the schedule between stops, to permit for doable variability in journey instances.
Lastly, let t0 be the dispatch time (departure time) of the primary car from a terminal.
Then, the timetable may be created merely utilizing the next construction, with n stops on the route and okay+1 automobiles to dispatch:
|Cease 1 (Terminal)||Cease 2||Cease 3||Cease 4||…||Cease n (Terminal)|
The first resolution variable right here is the preliminary dispatch time, t0. Completely different working situations would possibly result in quite a lot of alternatives for t0:
- “Clockface” values. Passengers might bear in mind the schedule extra clearly if the dispatch instances fall at simply acknowledged instances on the clock. For instance, with 15-minute headways, there could also be worth to passengers in dispatching a car on the :00, :15, :30, and :45 of every hour.
- Coordination for improved car scheduling. When a car finishes its journey at a terminal, it would typically be rotated to proceed onto the subsequent journey in the wrong way on the route. On this case, there’s a want for ample layover time on the terminal. If the car finishes a visit at time t, then completes the layover after a further time tL, then the car might begin its return journey after t + tL. Selecting the dispatch time to happen at or barely after t + tL permits for greater car utilization.
- A technique of visualizing such a system makes use of a so-called “string diagram,” proven on this determine. The blue traces point out the trajectory of a car from the terminal at cease 1 to the terminal at cease n, with brief dwell instances at every cease. Automobiles arriving at cease n then can return alongside the route in the wrong way (the crimson traces), after a layover (indicated by the black arrows). These diagrams may be helpful in visualizing car actions and crosses alongside the route.
- Coordination of passenger transfers. In some instances, it might be fascinating to decide on the dispatch time in order that passengers might hook up with different routes within the community with out unduly lengthy ready instances for the switch route. To do that persistently throughout the timetable, the 2 (or extra) routes that join for the switch should have the identical headway h. If that is so, then the preliminary dispatch time t0 may be chosen in order that the car’s arrival time on the switch level matches that of the car on the connecting route.
- Discount of auto necessities. The timetable will dictate what number of automobiles are in operation at any time of the day. In some instances, minor changes within the dispatch instances, coupled with modifications in layovers and/or dead-heads of automobiles between terminals can result in a discount within the variety of automobiles wanted for service.
Automobile scheduling, additionally referred to as “blocking”, includes assigning automobiles to cowl the journeys related to the timetable. A car “block” is the schedule of journey of a car for a given day, together with: (1) a pull-out from the depot, (2) a sequence of journeys from the timetable, (3) any dead-head journeys, and (4) a pull-in again to the depot (recall the car cycle from the unit on car operations).
Usually, as soon as the timetable is created, the time and mileage that automobiles spend in income service (i.e., finishing the journeys within the timetable) is fastened. So, the same old purpose in car scheduling is to attenuate the time and/or distance that automobiles spend outdoors of income service: e.g., pull-ins, pull-outs, dead-heads, and layovers. These all characterize time or mileage which might be “unproductive”, and therefore must be minimized.
Constraints on this course of embrace the next:
- Every journey within the timetable should be made by a car.
- A car can’t be assigned a couple of journey at any cut-off date.
- If a car should be re-positioned for a visit, the related journey time and distance from its present place to the brand new place should be noticed.
To unravel for the car schedule, one would possibly think about a easy “first-in-first-out” rule. On this case, a car stays on the identical route all through the entire interval, and is all the time assigned to the subsequent journey after a layover. The string diagram above provides simply such an association.
As a easy instance, suppose we’ve got a route that runs from terminal A to terminal B after which again to terminal A. Journey time from A to B and from B to A, together with operating and dwell time, is 30 minutes, and a minimal 5 minute layover is required at every terminal. Headways are 15 minutes.
Beneath is a timetable for this case, for journeys between 6:00 am and after 9:00 am. The left-hand aspect of the timetable exhibits car journeys from A to B, whereas the right-hand aspect exhibits car journeys from B to A.
The colours correspond to totally different automobiles used on the route. The grey shade corresponds to the primary car of the day, leaving A at 6:00 am and persevering with with the journey from B at 6:40, the journey from A at 7:15, and so on. A complete of 5 automobiles are required to cowl all of the journeys on this timetable.
Along with the journeys from the timetable, the car block additionally features a pull-out and pull-in, in order that the ultimate block for the primary car (grey) might appear like the next.
For networks with longer coverage headways (e.g., 30- or 60-minute headways), longer layovers at terminals could also be vital if automobiles serve the identical route all through the block. In consequence, different choices may be thought-about, notably by way of shifting automobiles from one route to a different. The timetable might enable automobiles to shift from one route to a different, with the intention to scale back layover time and/or to keep away from pull-outs or pull-ins. Particular actions within the block can embrace:
- Interlining: the method of switching a car from one route to a different at a terminal, when the routes share that widespread terminal.
- Deadheading: the method of switching a car from one route to a different, additionally requiring a re-location of the car (touring empty) to a different terminal.
These strategies may be fairly efficient below totally different timetabling situations.
Crew scheduling (additionally referred to as “run-cutting” within the transit business) is the duty of figuring out work shifts (so-called “duties” or “runs”) for operators. Usually, the first curiosity in crew scheduling is to attenuate the entire price of labor that meets the service necessities.
A major fraction, usually 60-70%, of the entire working prices at a transit company includes the price of operators, together with wages, advantages, and different premiums. With this in thoughts, small reductions within the variety of operators, or within the whole work hours, may end up in extra substantive reductions within the whole working price. For that reason, the duty of scheduling crew to automobiles is one space the place many massive transit companies can obtain some efficiencies and potential price financial savings.
Crew scheduling is sophisticated as a result of operators typically can’t merely be assigned to a car for all the car block. First, the shift would typically be for much longer than a typical 8-hour work interval; and, second, the operator might not get ample break time throughout car layovers (e.g., for lunch). As an alternative, the duties have to think about extra sensible considerations of the operators.
On this regard, transit companies have guidelines that dictate the sort of work shifts the operators might carry out. Normally within the US, the varieties of work shifts are ruled by collective bargaining agreements (union work guidelines) that specify work situations for transit operators. Attainable examples of labor guidelines might embrace restrictions like the next:
- An obligation ought to begin and finish on the similar terminal
- Crew wants not less than 2 breaks through the day: a traditional (15-min) break and a (30-min) lunch break
- A break is required after not more than Three hours of labor
- Every crew should have not less than Eight hours off earlier than resuming duties on the subsequent day
- Solely 20% of duties may be longer than 9 hours
- Solely 25% of duties may be break up into intervals with an unpaid break (e.g. an obligation that solely covers the AM and PM peak durations)
- Solely 30% of duties may be lined by part-time operators
The final method to making a crew schedule begins by reducing every car block into “items of labor.” Every bit of labor is a subset of journeys within the block, forming the basic unit of labor (driving) for the operator. Then, in accordance with the constraints from the work guidelines, these items of labor are assembled into possible duties. The hope is to assemble a full set of duties such that each one items of labor are lined and that the entire price is minimal. The price of an obligation can depend upon each the standard hourly price of pay for the operator for hours labored. If the operator has a straight shift (no unpaid break), they’re paid a specific amount, normally at a given hourly price. Different prices can embrace:
- A minimal assure of hours of pay, if the assure exceeds the variety of hours labored (e.g., Eight hours of pay, even when the operator works solely 7 hours);
- Premiums for additional time (e.g., time within the responsibility over Eight hours);
- Premiums for unfold time. Unfold is the entire time between the beginning and finish of an obligation. If this exceeds a sure most (e.g., 9 hours), the operator is entitled to further pay;
- Premiums for swing. Swing happens when the responsibility begins and ends at totally different places (terminals, depots);
- Premiums for break up duties, the place the responsibility has an unpaid break. This could happen when an operator works solely the AM and PM peak durations, with out working within the mid-day;
These guidelines on pay recommend that the crew schedule ought to comprise as many straight duties as doable. Small items of labor that stay after producing these straight duties may be allotted to part-time operators (if they’re obtainable), to keep away from different premiums, or lined utilizing break up duties with related break up and/or unfold penalties.
A second downside in crew scheduling is rostering, during which duties are assembled into a gaggle of duties (the “roster”) for every operator, by week. For instance, one roster might embrace the identical 8-hour responsibility for five weekdays. Nonetheless, many doable combos of duties may very well be thought-about, particularly if weekend or night service is offered. As soon as the rosters are created, operators select from amongst these responsibility rosters.
- Block: the sequence of journeys made by a car in the middle of someday of operations, together with each income and non-revenue journeys.
- Responsibility (or, Run): a piece shift for an operator for someday.
- Assure: the minimal pay hours for an operator, whatever the variety of hours labored.
- Piece of labor: an operator work task extracted from a car block.
- Reduction: the change of operators throughout a car block.
- Roster (additionally, rostering): the set of duties for a single operator in every week.
- Break up: an obligation overlaying not less than two intervals of time with an unpaid break.
- Unfold: the time between when an operator studies for responsibility and after they finish their responsibility.
- Straight: an obligation overlaying a single interval of time.
- Swing: an obligation during which the operator begins and ends at totally different places.
- Tripper: a brief work task (e.g., 2–Four hours); usually a lot shorter than a typical straight.
Avishai Ceder (2007). Public Transit Planning and Operation: Idea, Modeling, and Apply. Oxford: Butterworth-Heinemann.
Transportation Analysis Board (2003). Transit Capability and High quality of Service Guide, Transit Cooperative Analysis Program, Report 100, 2nd Version. 
- Transportation Analysis Board (2009a). Controlling System Prices: Primary and Superior Scheduling Manuals and Up to date Points in Transit Scheduling, Transit Cooperative Analysis Program, Report 135. 
- Transportation Analysis Board (2009b). Controlling System Prices: Primary and Superior Scheduling Manuals and Up to date Points in Transit Scheduling, Appendix, Transit Cooperative Analysis Program, Report 135 Appendix.