Routing & Scheduling
Routing & Scheduling
Introduction to Routing & Scheduling
Private firms that undertake the distribution of their goods to customer locations, and public transportation authorities responsible for the provision of transportation services to users both rely upon a fleet of vehicles and associated crews.
The effective management of these vehicles and crews gives rise to a variety of problems generally subsumed under the heading of “routing and scheduling problems”
Entities in Routing & Scheduling
The main entities in routing and scheduling comprised of resource characteristics, demand characteristics and road network characteristics.
Resource characteristics involves three another characteristics
- Depot characteristics
- Crew characteristics
- Fleet characteristics
Depot characteristics involve the factors such as capacity in which number of vehicles that can be housed in a depot. Single/multiple means number of available depots to house vehicles and service area is the assigned geographical area serviced by each depot.
Crew characteristics involves the instructions that should followed by the crew members. Maximum Shift Time is the maximum allowed time for driving and other driving restrictions includes Driver’s break (usually in the middle of the shift) and maximum continuous driving etc.
Fleet characteristics include factors such as size, types and capacity. Size is the number of available vehicles (fixed or variable). Types of fleet come with homogeneous, heterogeneous, special vehicle types and outsourced fleet. Capacity is the available space for carrying products (related to the type and kind of the products), weight or volume limitations, compatibility with product types (perishable goods, dangerous materials, etc.)
The entire characteristics involves in demand is based on customers. For each customer demand varies according to location in which address and geographical location of the customers are mentioned, nature of demands includes Deterministic, stochastic, partial satisfaction of demand of customers are allowed, Types of demand comes with Pick-ups, deliveries and mixed split deliveries. Special requirements involves scheduling of time windows, load/unload service times.
Road Network characteristics
Road network includes the characteristics such as types of networks which comprises of directed, undirected, mixed and Euclidean. Next is traveling time which comes with deterministic, stochastic and it is based on traffic conditions. Finally vehicle restrictions, in which certain areas that some specific types of vehicles are forbidden.
Costs related with Routing & Scheduling
Costs related to routing and scheduling is divided into variable costs and fixed costs. Variable costs are calculated on the basis of kilometers, in which vehicles cost and personnel costs are involved. Fixed costs are calculated on an annual basis including vehicle cost and personnel costs are included. Other costs may include the utilization of third-party (hired) fleets.
Routes, generally, are characterized by the geographical coverage (long, short), demand characteristics (high/ low volumes, service times, etc.), degree of dynamism (different/ same customers every day, etc.) and the underlying road network.
There are three (3) main types of routing networks Petal, Radial and Peripheral.
In petal network, each vehicle serves specific customers, usually used for dispersed customers with less-than truck load demand.
In radial network, each vehicle serves one or a limited number of customers, usually used for customers with large demands (close to or equal to truckload).
And in peripheral network, each vehicle serves specific dispersed geographical regions (line-haul) with high density of demand (commercial areas, hubs, etc).
Routing policies are based on geographical, demand and scheduling characteristics, which are specific for each company and customer.
Routing policies are divided into three: Fixed, variable and mixed.
Fixed routing policy
In fixed routing policy, the vehicles visit specific areas (and so customers) in specific days; customer demands are adapted to the scheduled routes. Examples are postmen and suppliers of minimarkets in rural areas.
Variable routing policy
In variable routing policy, where routes are designed based on the known demands. Examples are courier services and taxi services.
Mixed routing policy
In mixed routing, both routing policies are followed by a fleet of vehicles.
Routing & Scheduling Problems
The Most Known Categories of Routing & Scheduling Problems are Shortest Path Problem, Travelling Salesman Problem, Vehicle Routing Problem, Arc Routing Problem and Vehicle Scheduling Problem.