Technical Appendix 6 - Information on deterrence parameters

Information on Deterrence Parameters

This document should be read in conjunction with section 10.4 of the Technical Annex part A.

Introduction

The purpose of this document is to present a series of deterrence parameters estimated by i) trip purpose; ii) user group; and iii) mode, for use in implementing continuous measures in accessibility planning (refer to sections 3, 4 and 10 of the Technical Annex A for additional information on continuous accessibility measures).

Within the continuous measures proposed for accessibility planning, the deterrent effect of travel time is modelled by means of a negative exponential function of the form exp(-?t) which is hypothesised to describe the relationship between travel duration and the likelihood of travel.

It is important to note that the following deterrence parameters apply only to journey time based continuous measures, which utilise a negative exponential deterrence function. For journey distance, cost or generalised cost based continuous measures new deterrence parameters will have to be estimated based upon local or national data. It is important to emphasise that the utilisation of the following deterrence parameters for non-time based continuous measures will result in incorrect and unrealistic accessibility indicators being produced from the local or strategic audits.

The remainder of this document outlines the calibration results for the deterrence parameters (?) estimated from the National Travel Survey by trip purpose, user group and mode, for use with time based continuous measures calculated from use of a negative exponential type deterrence function. The tabulated sub-groupings of variables are statistically significant (with a 95% confidence).

In the absence of deterrence parameters estimated from local travel diaries/surveys information from the following tables should be used when implementing time based continuous measures. The DfT will utilise deterrence parameters contained within this document when calculating the continuous formulation of the core indicators.

When selecting a deterrence parameter from the following tables local authorities must ensure that the parameter selected or used is relevant for:

the population group being considered;
the service or facility under consideration; and must ensure that
the nature of the impedance term is consistent with that used in the calculation of the deterrence parameter. The impedance parameters presented in tables 1-4 inclusive can ONLY be used for journey time based continuous measures. That is they CANNOT be used for journey cost or journey distance based continuous measures.

If all these three conditions are not satisfied then the results obtained from application of the deterrence parameter to a continuous measure will be incorrect.

Local accessibility indicators may be developed by authorities may incorporate vulnerable at-risk population groupings or destination types which are not encompassed in the tables that follow. In such instances local authorities are encouraged to derive local deterrence parameters for the population groupings and services in question by commission targeted local travel or activity diary surveys for the population groupings and services in question.

Table 1: Summary Deterrence Parameters (?) by Gender, Location Type, Trip Purpose & Mode of Travel

	To Work	To Learning				To Local Centres		To Healthcare
Group	All	Age 5-10	Age 10-15	Age 5-15	Age 16-19	All	0 - car households	All	0 - car households
All	0.038	0.082	0.051	0.054	0.037	0.071	0.080	0.042	0.042
Male	0.034	-				-		0.039	0.043
Female	0.043	-				-		0.042	0.056
Area Types:
Inner London	0.053	-				0.072	0.067	-
Outer London	0.044	-				0.073	0.083	-
Metropolitan Areas	0.044	-	0.047	0.048	0.033	0.081	0.082	0.056	0.056
Urban Areas > 25k-	0.036	-	0.052	0.055	0.040	0.085	0.092	0.061	0.060
Urban Areas <25k and Rural	0.030	-	0.068	0.072	0.035	0.065	0.059	0.031	0.027
Modes:
Bus	0.044	0.076	0.050	0.052	0.046	0.070	0.082	0.047	0.048
Light Rail/ Underground	-	-				-		-
Rail	-	-				-		-
Taxi	0.054	-				0.12	0.13	0.097	0.12

Deterrence parameters are applicable to a time based continuous measure, which uses a negative exponential function.

Table 2: Deterrence Parameters (?) by Mode of Travel & Trip Purpose

	Com-muting	Work	Edu-cation	Food Shop-ping	Non-Food Shop-ping	Personal Business	Leisure	Escort-ing
All	0.038	0.021	0.045	0.071	0.042	0.034	0.031	0.042
Bus	0.044	0.034	0.051	0.072	0.055	0.040	0.039	0.051
Metro / Light Rail	0.052	0.044	0.033	0.048	0.044	0.052	0.048	-
Rail	0.033	0.0082	0.028	-	0.027	0.016	0.016	-
Taxi	0.054	0.060	0.041	0.12	0.19	0.099	0.094	0.10

Deterrence parameters are applicable to a time based continuous measure, which uses a negative exponential function.

Table 3: Deterrence Parameters (?) by Trip Purpose & Gender

	Com-muting	Work	Edu-cation	Food Shop-ping	Non-Food Shop-ping	Personal Business	Leisure	Escort-ing
Male	0.034	0.017	0.044	0.073	0.041	0.039	0.031	0.054
Female	0.043	0.025	0.037	0.073	0.042	0.043	0.032	0.040

Deterrence parameters are applicable to a time based continuous measure, which uses a negative exponential function.

Table 4: Deterrence Parameters (?) by Trip Purpose & Location Type

	Com-muting	Work	Edu-cation	Food Shop-ping	Non-Food Shop-ping	Personal Business	Leisure	Escort-ing
Inner London Built-up Area	0.053	0.033	0.031	0.072	0.048	0.038	0.035	0.040
Outer London Built-up Area	0.044	0.015	0.026	0.073	0.047	0.036	0.031	0.040
Metropolitan Areas ¹	0.044	0.041	0.050	0.081	0.051	0.056	0.041	0.043
Urban Areas 25k - 250k+	0.036	0.013	0.042	0.085	0.049	0.042	0.030	0.073
Small Urban Areas <25k and Rural	0.030	0.014	0.049	0.067	0.037	0.039	0.029	0.061

Deterrence parameters are applicable to a time based continuous measure, which uses a negative exponential function.

¹ Glasgow, Greater Manchester, Liverpool, Tyneside, West Midlands, West Yorkshire

Technical Appendix 6 - Information on deterrence parameters

Information on Deterrence Parameters

Introduction

Policy, guidance and research

Department for Transport

Transport agencies

Transport bodies

UK Government

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