Deterrence factors

A deterrence factor is some form of barrier to transportation, for example, time, cost, reliability, safety and security, physical features, quality, environment and information available.

The aim is to represent each deterrence factor or barrier as they are perceived by each population group. This must include the relative deterrent effect of different types of travel, and the costs associated with each (eg the greater deterrent effect of time waiting for a vehicle when compared with the same time spent travelling in a vehicle). Deterrence factors can be categorised as in table 3.1.

Table 3.1      Deterrence factors



Time factors

·       Travel time including walk time, wait time and in vehicle time

·       Scheduling of activities and transport services by time of day

·       Time budgets available to each population group for each trip type

Cost factors

·       Public transport fares

·       Fuel and vehicle costs

·       Affordability for the people concerned


·       Uncertainty about journey times

·       Uncertainty about journey quality, eg availability of a seat

Safety and security

·       Real and perceived security

·       Barriers during hours of darkness such as lack of street lighting

·       Real and perceived safety at all points in the journey including interchanges between modes

·       Presence of road crossing facilities

·       Speed limits

Physical features

·       Kerbs and physical obstructions

·       Steep hills and topographic constraints

·       Surfacing and maintenance

Quality and environment


·       Attractiveness and aesthetics of walking routes

·       Opportunities for shelter from weather and for rest points

·       Comfort of waiting areas and vehicles

·       Assistance and helpfulness of public transport staff

·       Support services when travelling, eg catering

Information and booking

·       Information available to plan journey

·       Time spent planning and booking journey

·       Availability of information during journey


Although these factors are presented separately it should be noted that eliminating one barrier to accessibility will not improve access if other barriers remain (DHC 2002). It is therefore usually necessary to look separately at the deterrence factors by people group. For accessibility to be improved, all relevant barriers for the people group being considered need to be overcome. This means public transport networks and network coverage is identified as an output from accessibility analysis rather than an input to the analysis.

Many trips will involve a combination of several modes, and for non-car available trips, the car options are excluded from the calculation. For example, a car available trip to a city centre from a rural area may involve a car leg to a park and ride site, a bus leg from the edge of the city to the centre and a walk leg from the bus terminus to the destination. The non-car available alternative would consider only the public transport, walking and cycling options to reach the city centre.

Operational factors, such as system capacity and congestion, need to be included in the analysis when appropriate.

The range of issues that can potentially be included in accessibility measures is broad and the number of accessibility indicators needed to represent people’s experiences could be very high. Practical application of the measures depends on selecting the critical issues and measures to capture the significant effects.