Robert Clear

Location Efficiency: Neighborhood and Socio-Economic Characteristics Determine Auto Ownership and Use - Studies in Chicago, Los Angeles and San Francisco

Auto ownership and mileage per car are shown to vary in a systematic and predictable fashion in response to neighborhood urban design and socio-economic characteristics in the Chicago, Los Angeles, and San Francisco regions. In all three cases, average auto ownership is primarily a function of the neighborhoods residential density, average per capita income, average family size and the availability of public transit. Similarly, the average annual distance driven per car is a strong function of density, income, household size and public transit, and a weaker function of the pedestrian and bicycle friendliness of the community. The similarity of these relationships among the three metro areas, despite their differences in geography and age, suggests that similar relationships may be consistent throughout the United States or worldwide. The application of the results to other metro areas is discussed. The dependence of driving on the policy-related variables of residential density, transit access, and pedestrian and bicycle-friendliness may provide policy makers with additional tools for reducing the costs and environmental impacts of transportation.

COST-EFFECTIVE VISIBILITY-BASED DESIGN PROCEDURES FOR GENERAL OFFICE LIGHTING

General office lighting visibility specifications were analyzed with respect to optimization of cost effectiveness. Cost effectiveness is a function of visual performance, not visibility per se. It was found that the present procedures which utilize ESI are not readily adaptable to cost optimization calculations. An alternative procedure using log VL is presented which appears suitable for this use. A sample calculation of net benefits versus light level is presented. For the same calculation the net benefits from visibility saturate at lower levels of visibility than are normally prescribed for office environments.

Analysis of a Visual Performance Experiment

The Smith-Rea check value verification experiment was reanalyzed. This experiment is one of the 20 experiments used to support the CIE 19/2 model. A preliminary data sheet from Smith and Rea listed an incorrect score function and contained a large number of arithmetic errors in converting raw times to scores. Correction of these errors changes the CIE fit. It is argued that the W/sub 123/ parameter of this fit is not related to the critical visual processes as claimed. The corrected data are used to examine basic trends. Subjects achieved their maximum scores for a large fraction of runs under all visibility conditions. There was no statistically significant difference in scores for tests from 100 to 5000 lux. Furthermore, illumination level was less important to performance than the other variables studied: subject, practice, and check set (legibility and contrast). The RQQ No. 6 recommended illumination levels for such tasks range from 200 to 750 lux, indicating that recommended levels may overstate the need for illumination.

A New Look at Models of Visual Performance

In this paper the authors argue that performance-visibility models are meaningless if “performance” is not strictly defined. The authors argument implies that there are serious conceptual problems in the new CIE visual performance model (CIE 19/2). They analyzed 1) optimization of performance with respect to time, 2) the problem of multiple tasks, and 3) the significance of ambiguous targets. The performance-visibility fits presented in CIE 19/2 are not correctly based on a physical model, and therefore in their present form should not be used as a basis for lighting recommendations.