Routing: Planning (Sequencing and Scheduling)

Question 1

Define planning/Loading, scheduling and controlling.

Answer 1

Planning: Determining what must be done and which activities precede others.
Scheduling: Determining when the tasks must be completed.
Controlling: Analyses and applied corrections to the difference between scheduled and actual performance.

Question 2

List the four planning and controlling activities.

Answer 2

1. Scheduling (When to do it?)
2. Sequencing (In what order?)
3. Loading (What to do?)
4. Monitoring and control (Is it going according to plan?)

Question 3

What is the goal of planning?

Answer 3

To have smooth operations.

Question 4

Give an example of a complex problem that makes it difficult to plan/schedule.

Answer 4

Travelling salesman.
e.g. 16 customer visits = 16! possible ways of visiting the customers.
Thus finding a high quality (or optimum) solution quickly becomes a key concern.

Question 5

Describe a tool that is used to produce a high quality solution to a difficult routing and scheduling problem.

Answer 5

Greedy Construction Heuristic (GCH).
This involves finding a solution by adding an element (e.g. customer visit) to the solution step by step using a ‘greedy’ criterion in a manner that minimises costs and/or maximises profit.

Question 6

Give a step by step Greedy Construction Heuristic guide for a Vehicle Routing Problem (VRP).

Answer 6

1. Start from the origin e.g. depot
2. Calculate the distance from the origin to all desired geographical points to be visited e.d. customer stops
3. Select the ‘Nearest Neighbour’ and add this selected point to the partially constructed route.
4. Select the last selected point and calculate the distance to the remaining points.
5. Select the ‘Nearest Neighbour’ and add it to the partially constructed route.
6. Repeat the process until all points have been reached.

Question 7

List the three factors to consider when using the Greedy Constructed Heuristic method.

Answer 7

1. Sequence of visits/stops
2. Timing of each visit: Exact time that the service will be delivered
3. Total fuel consumption/Travel costs derived from the travelled distance

Question 8

Give three examples of scenarios that might occur while considering the output of a Greedy Construction Heuristic application.

Answer 8

1. Work shift may not be sufficient to cover all stops (Multiple Travelling Salesman problem)
2. Certain items must be picked-up/delivered but the vehicles with limited capacity are used (Vehicle Routing Problem)
3. Specific customers must be visited at a specific date and time by specialised staff (Vehicle Routing Problem with Time Windows)

Question 9

In the class example, what are two major steps to consider when trying to solve a Vehicle Routing Problem listed in the previous card?

Answer 9

1. Assign the item with the highest capacity to the vehicle with the highest capacity.
2. Select the ‘Nearest Neighbour’ using the result from the previous step and see if the assigned clusters to each vehicle remains the same.

Question 10

List down the rules of sequencing.

Answer 10

1. Physical constraints (e.g. activities that use paint)
2. Customer priority (e.g. priority banking service)
3. Due date
4. Last In First Out
5. First In First Out
6. Longest Operation Time
7. Shortest Operation Time First
8. Judging sequencing rules (Judging based on performance objectives: dependability, speed, cost, quality, and flexibility)

Question 11

List down the types of scheduling.

Answer 11

1. The complexity of scheduling
2. Forward and backward scheduling
3. Gantt charts
4. Scheduling work patterns e.g. staff rostering

Question 12

List down the types of controlling.

Answer 12

1. Push and pull control

2. Drum, buffer, rope. (Comes from the Theory of Constraints and Optimised Production Technology)

Question 13

List the two types of demand.

Answer 13

1. Dependent demand

2. Independent demand

Question 14

What is the P:D ratio?

Answer 14

This is the time it takes the customer to wait for the product/service compared to the total time it takes to carry out all the activities required to avail the product/service to the customer.