Size and sign of time savings

INTRODUCTION The conventional approach in the U.K. has been to value all travel time changes at a constant rate regardless of their size or direction. This ‘constant unit value’ approach was supported by the 1980-86 UK DoT Value of Time Study (MVA/ITS/TSU, 1987). However, there has always remained a vocal body of opinion critical of this approach (see Welch and Williams, 1997, for references and discussion). Some of the main objections have been the following: i. small amounts of time are less useful than large amounts; ii. small time savings (or losses) might not be noticed by travellers and any that are not noticed cannot be valued by those affected and so should not be valued by society; iii. small time savings are said to often account for a large proportion of scheme benefits, so that small errors in measurement might mean that the scheme is really of no benefit to anyone; iv. allowing small time savings to have ‘full’ value is said to inflate the measured total of benefits and so lead to schemes (often road schemes) being wrongly found to have sufficient net benefit to justify implementation; v. time savings are less highly valued than are time losses, according to surveys, and so should have a lower unit value when evaluating schemes. Both aspects relate to the possible non-constancy of the value of time for a given journey made for a given purpose (clearly, it is much less controversial, and indeed standard practice, to allow for variation by purpose and traveller type). The practical difficulties are twofold. On the one hand, it is difficult to overcome the lay reaction that small time savings have little or no value, as well as the feeling that losses are more important than gains. On the other hand, if these points have any empirical relevance, they cause major problems for the cost-benefit calculus, as losses and gains will not cancel out, and time savings cannot be directly aggregated. Although they do not recommend that values differentiated by size and sign should be used for appraisal, the HCG/Accent (1999) Report (AHCG) notes that [p 259] "For any level of variation around the original journey time, gains (savings) are valued less than losses. For non-work related journeys, a time savings of five minutes has negligible value." A recent paper by Gunn (2001) notes that corroborative results are available from a reanalysis of the 1988 Dutch value of Time study. For reasons which will be carefully rehearsed in this paper, we do not believe that the conclusion on the differences between gains and losses is safe. This is based on an extensive re-analysis of the AHCG data. We have found it harder to reach a conclusion on the issue of small time savings, we agree with AHCG that their data undoubtedly implies a lower valuation: we have some concerns, nonetheless, as to the interpretation which should be placed on this

Size and sign of time savings

INTRODUCTION The conventional approach in the U.K. has been to value all travel time changes at a constant rate regardless of their size or direction. This ‘constant unit value’ approach was supported by the 1980-86 UK DoT Value of Time Study (MVA/ITS/TSU, 1987). However, there has always remained a vocal body of opinion critical of this approach (see Welch and Williams, 1997, for references and discussion). Some of the main objections have been the following: i. small amounts of time are less useful than large amounts; ii. small time savings (or losses) might not be noticed by travellers and any that are not noticed cannot be valued by those affected and so should not be valued by society; iii. small time savings are said to often account for a large proportion of scheme benefits, so that small errors in measurement might mean that the scheme is really of no benefit to anyone; iv. allowing small time savings to have ‘full’ value is said to inflate the measured total of benefits and so lead to schemes (often road schemes) being wrongly found to have sufficient net benefit to justify implementation; v. time savings are less highly valued than are time losses, according to surveys, and so should have a lower unit value when evaluating schemes. Both aspects relate to the possible non-constancy of the value of time for a given journey made for a given purpose (clearly, it is much less controversial, and indeed standard practice, to allow for variation by purpose and traveller type). The practical difficulties are twofold. On the one hand, it is difficult to overcome the lay reaction that small time savings have little or no value, as well as the feeling that losses are more important than gains. On the other hand, if these points have any empirical relevance, they cause major problems for the cost-benefit calculus, as losses and gains will not cancel out, and time savings cannot be directly aggregated. Although they do not recommend that values differentiated by size and sign should be used for appraisal, the HCG/Accent (1999) Report (AHCG) notes that [p 259] "For any level of variation around the original journey time, gains (savings) are valued less than losses. For non-work related journeys, a time savings of five minutes has negligible value." A recent paper by Gunn (2001) notes that corroborative results are available from a reanalysis of the 1988 Dutch value of Time study. For reasons which will be carefully rehearsed in this paper, we do not believe that the conclusion on the differences between gains and losses is safe. This is based on an extensive re-analysis of the AHCG data. We have found it harder to reach a conclusion on the issue of small time savings, we agree with AHCG that their data undoubtedly implies a lower valuation: we have some concerns, nonetheless, as to the interpretation which should be placed on this

Market segmentation analysis

INTRODUCTION This working paper presents the findings of research aimed at assessing differences in the value of time by market segment. It draws on findings presented in AHCG’s final report to DETR (AHCG, 1996) and previous research conducted during the course of this research contract (Bates and Whelan, 2001) and it is intended that this document be read in conjunction with those two reports. The paper describes the estimation of a base model for each journey-purpose (business, commuting and other) and shows how each is influenced by: income, journey distance, cost reimbursement, congestion, vehicle occupancy, trip sub-purpose, occupation, age group, gender, household type, ‘free time’, respondent type, time constraints and geographical region. The findings of this analysis are then drawn together to develop a final set of models that allow the value of time to vary across a range of market segments. All models are estimated using GAUSS (Aptech Systems) without taking account of the repeat observations nature of the stated preference data

A STATISTICAL ANALYSIS OF THE IRISH ELECTORAL REGISTER AND ITS USE FOR POPULATION ESTIMATION AND SAMPLE SURVEYS. General Research Series Paper No. 130, July 1986

The Electoral Register’s prime purpose is to serve as a list of those persons in tile State who are eligible to vote in national and local elections. Apart from this function it is also used by researchers in the social sciences for other purposes, as it is tile only regularly updated list of the adult population which is readily available. In particular, it has been used as a sampling frame for social surveys and as an indicator of population levels. The accuracy of the Register is, therefore, of interest to researchers

Stochastic Gravitational Wave Measurements with Bar Detectors: Dependence of Response on Detector Orientation

The response of a cross-correlation measurement to an isotropic stochastic gravitational-wave background depends on the observing geometry via the overlap reduction function. If one of the detectors being correlated is a resonant bar whose orientation can be changed, the response to stochastic gravitational waves can be modulated. I derive the general form of this modulation as a function of azimuth, both in the zero-frequency limit and at arbitrary frequencies. Comparisons are made between pairs of nearby detectors, such as LIGO Livingston-ALLEGRO, Virgo-AURIGA, Virgo-NAUTILUS, and EXPLORER-AURIGA, with which stochastic cross-correlation measurements are currently being performed, planned, or considered.Comment: 17 pages, REVTeX (uses rcs, amsmath, hyperref, and graphicx style files), 4 figures (8 eps image files

Ergonomic Standards for Pedestrian Areas for Disabled People: Methodology and Sample Identification

This project is a TRRL research contract, the aim of which is to produce guidance on the design of pedestrian areas and footways for elderly and disabled people. The first part of the project was a literature review and consultation exercise, the objective of which was to identify key impediments for investigation. The second part of the project involved the detailed survey work on the key impediments. This Working Paper reports upon the development of the second part of the project and, in particular, upon the identification of the sample of disabled people to be used in the detailed interview and observation work. The sample identification involved contacting some 3000 disabled people listed in official disability registers, and 250 ablebodied people via on-street interviews. From the disabled sample approximately 500 people were interviewed in order to find out more about their disability and to assess the usefulness of a preliminary disability categorisation system; their activity rate; problems they experience in using pedestrian areas and footways; and their willingness to take part in further stages of the study. From the interviews, a sample of people in each of the revised categories, together with samples of the elderly and the ablebodied, were selected for an observation phase in which those involved were observed completing a movement distance exercise, and using different types of pedestrian facility, in central Leeds

Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\dot{M}_{out}$/$\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\sim$ 20$^{\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($\dot{M}_{out}$/$\dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]\lambda \lambda 6716,6731$ lines and is detected out to $\sim$ 1\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log($\dot{M}_{acc}$) [M$_{sun}$/yr]= -10.6 $\pm$ 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow $\dot{M}_{out}$ was derived for a range of values of A$_{v}$, up to a value of A$_{v}$ = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow ($\dot{M}_{out}$) was estimated in the range -11.7 to -11.1 for both jets combined. Thus $\dot{M}_{out}$/$\dot{M}_{acc}$ [\Msun/yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the H$\alpha$ line show that the bulk of the H I emission comes from the accretion flow.Comment: accepted by Astronomy & Astrophysic