Trends in Single Occupant Vehicle and Vehicle Miles of Travel Growth in the United States Final Report (1998) / Chapter Skim
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4. SUMMARY AND CONCLUSIONS
4. SUMMARY AND CONCLUSIONS
Pages 52-60
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From page 52... ...
The results of the analysis indicate that development patterns, vehicle availability, and price and service levels are all important determinants of mode shares and occupancies. Specifically, the models indicate that transit service levels can have a significant impact on SOV shares, and that downtown parking prices are also a powerful deterrent to driving alone.
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From page 53... ...
Public policies a/one are not the culprit The modeling results confirm our assertion in Chapter ~ that much of the trends in market shares and occupancies that have been observed in the last twenty years can be explained by factors that are beyond the direct control of transportation policymakers. Few would argue, for example, that the decline in household sizes that appears to have made carpooling less attractive is the direct result of transportation-related policy, given that the causes of this decline stem primarily from changes in family structure.
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From page 54... ...
The mode} results indicate that at least 50% of the variation in the observed SOV share can be explained by changes in relative prices, accounting for both of the cost of the private vehicle mode as well as the cost of competing transit service. The static 1990 models also inclicate that parking prices are an important factor in explaining transit market share.
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From page 55... ...
This is particularly good news, considering that we have argued that it is in large part these underlying socioeconomic and demographic forces that are ultimately compelling the shift away from high occupancy modes and the consequent rise in vehicle trips and congestion. While the data of Chapter ~ show that for some time household sizes have been declining, again in response to underlying demographic changes, a reexamination of Table ~ shows that total workers per household has in fact remained more or less constant, actually increasing slightly in 1990.
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From page 56... ...
Average Household Size 1970-2010 3.2 3.1 - _ 3.0 2.9 2.8 - _ 2.7 2.6 2.5 , 1 , , \ 1970 1980 1990 2000 2010 Source: US Bureau of the Census, 1996. Labor Force Population .................
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From page 57... ...
A brief review of summary results from the 1995 NPTS suggests that the interpretations in this report remain valid today, and are consistent with our conclusions about the future of the trends examined (the results show that vehicle availability is saturating and that occupancies may have stabilized, for example)
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From page 58... ...
Given that we have in our analysis found evidence that transit service levels may be important in mode choice decisions, but were unable to identify the independent effects of transit service levels in several market segments, additional analyses, perhaps using a more sophisticated simultaneous equations framework, could be very useful. Further, examination of the effect of transit capacity, particularly during the peak period when high load factors can cause marked changes in service quality, might provide additional important insights.
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From page 59... ...
As described in Chapter i, the constraints of this study prevented us from performing a more detailed and thorough analysis of trends in mode shares at Suburb-regional levels of geography. Such an analysis might involve comparing shares for specific commuting flows such as the suburb to central city market for specific metropolitan areas over time with identical geographies.
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