Abstract
The author considers that the variations observed in transport demand elasticities may be due to non-symmetric price effects or hysteresis in the demand relationship. She proposes that consumers may not respond in the same way to rising and falling prices, as is traditionally assumed, but react in a more complex fashion related to previous price history. Research is described which suggests that consumers react more strongly to rising than falling prices and to substantial as opposed to minor rises. This implies that traditional demand models produce average price elasticities which are not adequate for predicting the effects of specific price changes at particular points in time.