As a necessary step in the analysis of possible future requirements for the New York City rapid transit system a model to estimate ridership in the system is developed. Analysis of historic data reveals that annual ridership on the system is positively related to employment in the Manhattan Central Business District (CBD) and to the level of transit service, measured in car-miles; it is negatively related to the number of autos registered in New York City and to the transit fare, measured in constant dollars. These four variables explain 80 percent of the year-to-year variation in ridership. The elasticity of demand with respect to CBD employment is found to be + 0.75, with respect to fare, - 0.12, with respect to auto registrations, - 0.25, with respect to service, + 0.13. Statistically, the relationship of subway ridership to fares and to CBD employment is very strong. The relationship to auto registrations is weaker and to service weaker still. The impact on ridership, if all auto commuters to the CBD are shifted to transit, is also examined suggesting that transit ridership would rise by about 10 percent. To explore alternative estimates of future ridership eight combinations of the independent variables are examined, including stable and declining CBD employment, stable and declining fares, and unconstrained and energy-constrained automobile ownership. The results suggest long-term changes in current ridership ranging from a 9 percent loss to a 34 percent increase.’
