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Scheduling
- 1. Rohit Parkar eMBA Roll No. 13055.
- 2. What is scheduling 1. Assigning an appropriate no of workers to the jobs during each day of work. 1. Determining when an activity should start and end, depend on its • Duration. • Predecessor activity (or activities ). • Predecessor relationship. • Resource availability. • Target completion date of the project.
- 3. In Production scheduling Companies use forward and Backward scheduling . • Forward Scheduling. • Backward Scheduling.
- 4. Objectives of Scheduling THROUGHPUT . TURNAROUND . RESPONSE TIME. OTHER RESOURCE USE. FAIRNESS. CONSISTENCY.
- 5. Other Scheduling objectives: Fairness to all processes Be predictable Minimise overhead Balance available resources Enforcement of priorities Achieve balance between response and utilisation Maximise throughput Avoid indefinite postponement and starvation Favour processes exhibiting desirable behaviour Degrade gracefully under heavy load.
- 6. There are three main Scheduling used: Long-term Scheduling -The long-term scheduling controls the degree of multiprogramming and decides on which job or jobs to accept and turn into processes. Medium-term scheduling-which determines which processes suspended and resumed?” Short-term Scheduling: Short term scheduling is concerned with the allocation of processor time to processes in order to meet some pre-defined system performance objectives.
- 7. Scheduling Levels : High level Scheduler (External priority) is responsible for deciding which job currently on disc are to be brought into memory. Low Level Scheduler (Internal Priority) is responsible for deciding which of the ready processes is to be run.
- 9. B E S T (Brihanmumbai Electric Supply and Transport) BEST bus started in the year 1907. Total 4680 busses. 365 routes. 25 depots (region wise). 22000 bus drivers and conductors. It is considered a second heart of the city.
- 10. BEST(Bus) SCHEDULING 1. Placement of the Bus Route. A. 1. 2. Route In New Area . proper route placementThe route creation process . Identify an area that needs new transit service Determine the terminus locations 3. Other factors Designing the route include the presence of other routes nearby and the type of street the bus will travel upon. Except in very dense areas, parallel bus routes should be no closer than 1/2 mile to each other. Speed bumps, speed humps, or traffic circles should also be avoided.
- 11. B. Route In Existing Area. Plan new bus routes operating in areas with existing coverage. These new routes are often have limited stop or express versions of existing local routes. Provide direct service between two trip generator. Service levels increase.
- 12. c. Placement of Bus Stops Appropriate distance between each bus stop. Placement of bus stops -the presence of trip generators, transfer opportunities with other routes, and pedestrian access. Adopting guidelines which allow for wider stop spacing offers several advantages to the transit system. Site visit to determine the actual placement at the intersection. Bus stops should be located at traffic signals, or at least marked crosswalks
- 13. D. Determination of Times for the Bus Each route will at the very least have two timing points: the start and end of the route. Optimum number of time points be selected for the route. For that 1. Estimate running time. 2. Calculate the overall cycle time can be determined.(Before and After )
- 14. E. Writing the Bus Schedule What our stops are. How long it will take to travel between our stops 1. Using computer scheduling software . The most important benefit of scheduling software lies in its run cutting function.
- 15. 2. For scheduling a particular route two things are important. The service span of the route . For existing route – we would consider a demand based service span based on the first and last trip. If no body was riding-reduce the service span. If a significant no. of people were riding-50 % or more-consider the service span.
- 16. 3. Policy based service span and the run cutting process. 1. Policy based service span- specific time periods. 2. The run cutting process- make it easier and more cost effective to schedule the drivers
- 17. The frequency/headway of the route. 1. Demand based headway. How often buses will pass by a particular point along the route. Minimum number of buses required per hour. Load factor- maximum number of passengers per bus, every seat is full no body is standing-i.e. in the ratio of 1.0 .
- 18. 2. Policy based headway. Operate a minimal level of service. All of their routes operate at least every thirty minutes whenever the subway is in operation. From 4.30 AM to 2 AM Monday through Saturday From 6 AM to 2 AM on Sunday.
- 19. Once the determination of service span and the headway the actual creation of the schedule is quite straightforward. By using scheduling software . 1. ESRI. 2. Hastus.
- 20. F. Blocking, Run Cutting and Rostering. Cutting the schedule. Blocking the trips. If the block operates out of closest depot- saves deadline time and money. Run cutting. Rostering.
- 21. THANK YOU
Editor's Notes
- In Production scheduling Companies use forward and Backward scheduling to allocate plant and machinery resources, plan human resources, plan production processes and purchase materials.Forward Scheduling is planning the tasks from the date resources become available to determine t he shipping date and due date.Backward Scheduling is planning the task from the due date or required by date to determine the start date and/or any changes in capacity required.
- Possible Scheduling Objectives:THROUGHPUT: Minimize total work done in a given (long) period of timeTURNAROUND: Minimize total time required for a single (typically long) task, such as a batch job.RESPONSE TIME: Minimize total time required for a single (typically short) task, such as a command.OTHER RESOURCE USE: Minimize use of other resources besides processor time, especially storage.FAIRNESS: Provide service appropriate related to the priority of each task, which may be established by external policies.CONSISTENCY: Besides minimizing resource use, it may be important to ensure consistent service over a set of tasks.Scheduling objectives:Fairness to all processesBe predictableMinimise overheadBalance available resourcesEnforcement of prioritiesAchieve balance between response and utilisationMaximise throughputAvoid indefinite postponement and starvationFavour processes exhibiting desirable behaviourDegrade gracefully under heavy load.
- BEST SCHEDULINGPlacement of the Bus Route Route In New Area As you can well imagine, proper route placement is the key to success of a given bus line. Before you begin the route creation process it is essentialto have a complete understanding of the existing route structure and demographic makeup of the service area for your new route. Many transit systems have service standards which dictate that a certain percentage of the service area's population and employment be a certaindistance from the nearest busstop, usually 1/4 mile.While there are likely to be certain parts of the service area that are without transit coverage, before new routes are operated in these areas demographic data must be consulted to make sure sufficient density exists to support service.Once you identify an area that needs new transit service, the first thing you should do is determine the terminus locations. Route termini need to, as much as possible, be significant trip generators. Examples include downtown areas, hospitals, universities, malls, and transfer centers. Sometimes the demographic data referenced above can identify areas that have robust housing or employment but are not obvious trip generators.At least one end of the route should have adequate layover facilities, including access to at least restrooms for the operators, and preferably refreshment opportunities. Not providing sufficient amenities at the end of the route will likely cause operators to stop at a mid-route bus stop to use restrooms and access refreshments. Of course, route termini that are on private property will need the approval of the property owner, which may be difficult to obtain. Once the two terminus locations are identified,selection of the route follows. As much as possible, the route should follow the shortest road distance between the two end points. From one bus stop to another bus stop.For example, if a route which has a running time of 60 minutes includes a deviation which takes 6 minutes of that time, then the total ridership generated by the deviation should be greater than 10% of the total. Other FactorsDesigning the route include the presence of other routes nearby and the type of street the bus will travel upon. Except in very dense areas, parallel bus routes should be no closer than 1/2 mile to each other. In addition, streets with traffic calming measures such as speed bumps, speed humps, or traffic circles should also be avoided. In many cases bus routes will have no choice but to traverse streets with some of the above conditions; thus, the judgment of the transit planner will have to come into play to make the best of a bad situation.
- B. Route In Existing AreaIn addition to operating service in entirely new areas, agencies sometimes plan new bus routes operating in areas with existing coverage. These new routes are often limited stop or express versions of existing local routes. Sometimes new local routes are created which provide direct service between two trip generators that currently require a transfer to access. In areas with existing service, the performance of existing routes is the paramount concern in route planning. Before inaugurating express or limited routes, you must make sure that corridor demand can support robust frequencies on both the limited and local routesTransit agencies sometimes are tempted to overlay routes on top of an existing grid system that provide direct access between two non-linear points. Operating a pure grid system is not only the easiest network for the public to understand, but it is also the most efficient to operate.An exception might be made if origin-destination surveys demonstrate that there are enough passengers going between the two destinations to independently support a special route. As new routes along existing corridors generally already have bus stops and terminus locations identified, there are easier to implement both operationally and politically. However, if overall service levels increase it is important to ensure that adequate layover space is available at least one of the terminals.
- Placement of Bus Stops The first factor that should be considered when placing bus stops is the appropriate distance between each one.The placement of bus stops approximately one-quarter mile apart from each other. In areas of higher density bus stops can be placed more frequently, but never nearer than one-eighth of a mile apart. Actual stop placement will be determined by a number of factors, including the presence of trip generators, transfer opportunities with other routes, and pedestrian access. Bus stops for express routes should be placed every 1/2 - 1 mile depending on intersecting bus routes and traffic generators. Adopting guidelines which allow for wider stop spacing offers several advantages to the transit system. First, fewer stops will definitely increase your operating reliability and possibly your operating speed as well. Customers are likely to view the route as much faster than one with more stops even if the travel time is the same.Second, fewer bus stops will result in lower maintenance costs for the company, as there will be fewer stops to clean. Third, fewer stops makes it more likely the company will have the budget to construct stop amenities such as benches, shelters, and real-time arrival information at each stop. Fourth - and this is a practical benefit - the fewer the stops the easier you will be able to have your stops approved by your city's Public Works department.Home owners, for example, do not generally want to have a bus stop right outside their door. Once you have tentatively placed your stops on a map, you should make a site visit to determine the actual placement at the intersection. Proper bus stop placement takes into account several factorsThe first order of business is to decide whether your bus stop should be located at the near side or at the far side of the intersection. Example:-whether to place stops at the near side or the far side of an intersection is whether the bus stop is in a traffic lane. If a bus stop is not in a traffic lane, then far side stops are preferred because doing so does not hamper vehicles from making right turns. However, if a bus stop is in a traffic lane, near side stops are preferred to avoid the danger of vehicle queuing behind a bus in the intersection. Many transit providers have bus stop design guidelines that specify when near and far side stops are to be used. Some transit systems like clustering stops at transfer points at two of the four corners to make transferring easier. Where possible, bus stops should be located at traffic signals, or at least marked crosswalks, in order to ensure that pedestrians can cross safely. Overall, bus stop location and placement is a sometimes difficult process that takes into account many different factors. Time spent on this step is worthwhile because the number and location of bus stops is a primary factor in determining the success of the route
- Determination of Times for the Bus .. In this part we will look at how we determine the time points of the route and how long the bus should take to drive between the time points.Each route will at the very least have two timing points: the start and end of the route. If bus drivers will be relieved at a particular location, then that location must be a time point as well. Additional time points should be added so that there is a time point approximately every 8 - 10 minutes of driving time, with more time points at the beginning versus the end of the route. Good locations for time points are major transfer points and significant trip generators - bus stops that are responsible for more than 10% of the total boarding’s for the entire route are good candidates for time points. It is very important that an optimum number of time points be selected for the route. Too many time points’ works to slow the overall bus speed down as drivers may drive excessively slowly in order to not arrive or depart from a time point early. Too few time points can encourage bus bunching as drivers may drive at different speeds from one another. Once time points are tentatively selected, the route needs to be driven in order to determine the running times required between each time point. estimate initial running time is to drive the route at a maximum speed of five mph below the speed limit. After obtain the time required to drive the route in this way I multiply the total by 1.3 to account for the time spent at bus stops picking and dropping off passengers.First, the entire route needs to be driven and the overall time, including the 1.3 multiplication factor, required to drive the route calculated. Next, the time required to drive between each time point should be calculated.Compare the summation of the time required to drive between each time point with the overall time required to drive the entire route; If the summation of the individual time point times is greater than the overall time then subtract running time evenly from the time required to drive between each time point, starting with subtracting time from the last time point before the route terminus to the terminus. If the summation of the individual time point times is less than the overall time then add running time evenly from the time required to drive between each time point, starting with adding time from the start of the route to the first time point after the start and so on. Normally, the route should be driven at several different times during the day in order to take into account the fact that running time varies by the time of day. At a minimum, the route should be driven during the A.M. peak period around 8 A.M., during the mid-day around 12 PM, during the P.M. peak period around 4:30 P.M., and at night around 8 P.M. On weekends the route should be driven twice: around 8 A.M. for the early A.M. / night time and around 2 PM for the afternoon time. When the cycle time is determined we can now able to determine how many resources the route will take to operate. Most transit systems decide the frequency of the route; once the frequency is determined the number of buses required to operate the route follow from simply dividing the cycle time by the frequency. Other systems, determine how many buses will operate along the route and determine the frequency by dividing the cycle time by the number of buses. Since the majority of transit system only operate routes on frequencies that are divisible by 60 (i.e. buses every 10, 15, 20, 30 or 60 minutes), it is desirable to operate routes that have cycle times that are in multiples of 30 - 60. Cycle times that do not fit this pattern will result in layover percentages that are either too high or too low, which will result in unproductive layover time or deadheading to different locations if interlining is not an option. Now that we know how long the bus will take to travel along our route and an idea as to how many resources will be required to operate the route, we are now able to write the schedule.
- 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 50 vehicles write bus schedules with the assistance of computer software. Currently two computer scheduling software packages dominate the market: ESIC and Hastus.The most important benefit of scheduling software lies in its run cutting function.
- 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. This paragraph is just for your information but it is important.If route operates along the same pathways as other routes, then a service span which includes only the peak periods may be acceptable. Otherwise 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.
- The frequency/headway of the route refers to how often buses will pass by a particular point along the route.Route headway is usually determined through either a demand or policy basis. If a headway is demand based, then the headway is determined by the minimum number of buses required per hour to make sure that a particular load factor is not violated. Recall that the load factor is the ratio of passengers to seats; i.e. a load factor of 1.0 means that every seat is full and nobody is standing. Most transit systems specify a maximum load factor of 1.5; BEST has a passenger capacity to carry 51 seats and 21 standees . Thus, to determine the demand based headway for each hour by dividing the total number of people passing the peak load point - the point along the route where the most people are on the bus, usually in the middle of the route - by our maximum number of passengers per bus determined by the load factor.For example, if six hundred passengers pass the maximum load point in an hour and we allow a maximum of sixty passengers on the bus, then our demand based headway is equal to 600 / 60 = 10 buses per hour for a headway of six minutes. If we used a 1.2 load factor then we would only allow 48 passengers on the bus, which would mean our demand based headway would change to 600 / 48 = 12.5 buses per hour for a headway of a little less than five minutes.
- Policy based headwayIn a policy based headway, operate a minimal level of service, otherwise wontoperate service at all. Many agencies, including Mumbai Metro, specify a policy headway of sixty minutes. In contrast, the Mumbai Transit Commission has set a policy that dictates that all of their routes operate at least every thirty minutes whenever the subway is in operation, which is from 6 AM to 2 AM Monday through Saturday and 6 AM to 2 AM on Sunday. Since a route operating a headway of less than thirty minutes is considered an unattractive service even for the transit dependent consider setting a policy based headway of thirty minutes.
- Once we have determined the service span and the headway the actual creation of the schedule is quite straightforward. Utilizing scheduling software we merely type in the list of times we desire the bus to arrive at a particular time point and the software automatically fills in the rest of the times based on the running times we measured. Once our schedule is finished it should undergo periodic maintenance.For example, a complete running time analysis should be done for all time periods and days every other year using either automatic vehicle location data or manual checks. The schedule changes of routes that intersect with this one should be monitored to make sure transfer connections are maintained. Finally, up to date ridership information should be reviewed to make sure the demand based headway does not have to be adjusted or that the policy based headway needs to become a demand based headway.
- 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: Cutting the 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 Depot. We repeat the process until every trip is in a block.Blocking is a much tougher process if the bus route operates very frequently than if the route operates infrequently. Also, if a bus routes operates out of more than one depot 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 depot to that starting and ending location doing this will save deadhead time and money. 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. 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