Many transit agencies use zone-based fares, peak period fares, bus passes, ride-free zones, and special fares for different user groups. The price elasticity of demand for transit is commonly estimated to be -0.3, meaning that a 50% reduction in transit fares will result in a 15% increase in transit ridership. Improving other factors such as the availability, quality, and/or frequency of transit service effectively complements the strategy of transit fare adjustments. Demonstrations of low or free transit fares in urban areas (Denver, Boston) have estimated area-wide VMT reductions of approximately 2%. The Puget Sound Regional Council estimates the potential vehicle trip reduction for transit service fare changes at 1.8% (PSRC, 1994. pp. 24-32). Case/Example: Denver (CO) and Boston (MA). Source/Reference: WSDOT, 2000, pp. 77-78.