1)Answer the questions.

1. What can you say about routing problems? How can they be solved?

2. What may be the different destination points?

3. What is “computational time”?

4. Is it possible to reduce transportation cost and improve customer service?

5. What is the range of transportation costs among general logistics costs?

2) Make word combinations using the following words.

1) routing	a) delivery
2) starting	b) method
3) test	c) source
4) grocery	d) problem
5) transportation	e) method
6) multiple	f) concern
7) shortest route	g) point
8) minimize	h) customer service
9) major	i) samples
10) to improve	j) time

3) Match the following terms with their definitions.

1) starting point	a) consignment of goods to be delivered
2) destination point	b) a car, truck etc used to deliver goods
3) shipment	c) difficulty or issue connected with delivery
4) routing problem	d) a place where goods are loaded to be transported
5) transport vehicle	e) a final point in a route

Part 3. Vehicle Routing and Scheduling.

Vehicle routing and scheduling (VRI) is an extension of the basic vehicle routing ("traveling salesman") problem. Realistic restrictions are now included such as (1) each stop may have volume to be picked up as well as delivered; (2) multiple vehi­cles may be used having different capacity limitations to both weight and volume; (3) a maximum total driving time is allowed on a route before a rest period of at least ten hours (Department of Transportation safety restriction); (4) stops may permit pick-ups and deliveries only at certain times of the day (called time windows); (5) pickups may be permitted on a route only after deliveries are made; and (6) drivers may be allowed to take short rests or lunch breaks at certain times of the day. These restric­tions add a great deal of complexity to the problem and frustrate our efforts to find an optimal solution. However, good solutions to such prob­lems can be found by applying principles for good routing and scheduling or some logical heuristic procedures. Consider the routing and scheduling problem where trucks are to start at a central depot, visit multiple stops to make deliveries, and return to the depot in the same day.

Principles for Good Routing and Scheduling

Decision makers, such as truck dispatchers, can go a long way toward developing good truck routes and schedules by applying eight guideline principles. These are outlined as follows.

1. Load trucks with stop volumes that are in the closest proximity to each other. Truck routes should be formed around clusters of stops that are nearest each other in order to minimize the interstop travel between them. This also mini­mizes the total travel time on the route.

2. Stops on different days should be arranged to produce tight clusters. When stops are to be served during different days of the week, the stops should be seg­mented into separate routing and scheduling problems for each day of the week. The daily segments for which routes and schedules are to be developed should avoid overlapping stop clusters. This will help to minimize the number of trucks needed to serve all stops as well as to minimize truck travel time and distance during the week.

3. Build routes beginning with the farthest stop from the depot. Efficient routes can be developed through building stop clusters around the farthest stop from the depot and then working back toward the depot. Once the farthest stop is identified, selecting the volume from the tightest cluster of stops around this key stop should be used to fill out the assigned truck capacity. After the stop volumes have been assigned to the vehicle, select another vehicle and identify the farthest stop from the depot among the remaining stops not yet assigned to a vehicle. Proceed in this manner until all stop volumes have been assigned to vehicles.

4. The sequence of stops on a truck route should form a teardrop pattern. Stops should be sequenced so that no route paths cross, and the route appears to have a teardrop shape. Recall Figure 7-6. Time window restrictions and the forcing of stop pickups after deliveries may cause route paths to cross.

5. The most efficient routes are built using the largest vehicles available. Ideally, using a vehicle large enough to handle all stops in one route will minimize total distance, or time, traveled to serve the stops. Therefore, the largest vehicles among the multiple sizes in a fleet should be allocated first, providing that good utilization for them can be realized.

6. Pickups should be mixed into delivery routes rather than assigned to the end of routes. Pickups should be made, as much as possible, during the course of the deliveries to minimize the amount of path crossing that can occur when such stops are served after all deliveries are made. The extent that this can be done will depend on the vehicle configuration, the size of the pickup volumes, and the degree to which they may block access to the delivery merchandise inside the vehicle.

7. A stop that is greatly removed from a route cluster is a good candidate for an alternate means of delivery. Stops that are isolated from the stop clusters, especially those with low volume, are served at great driver time and vehicle expense. Using small trucks to handle such stops may prove to be more eco­nomical, depending on the isolation of particular stops and their volumes. Also, using a for-hire transportation service would be a good alternative.

8. Narrow stop time window restrictions should be avoided. Time window restrictions on stops, where they are narrow, can force stop sequencing away from ideal patterns. Since time window restrictions are often not absolute, any stop(s) forced to be served in a less-than-desired routing pattern should have its time window limits renegotiated and hopefully widened.

Such principles as these can be easily taught to operating personnel to produce satis­factory, although not necessarily optimal, solutions to realistic routing and schedul­ing problems. They provide guidelines for good route design, yet operating person­nel still have the latitude to deal with the restrictions not directly accounted for in the methodology or the exceptions (rush orders, road detours) that can occur in any truck operation. Route designs developed in this manner can offer substantial improvements over otherwise unschooled routing and scheduling methods.

Exercises.