People still talk about the 7/7 effect on cycling in London — the theory that fear of terrorism and/or the weeks of disruption that followed the bombings led to people taking up cycling in London. I'm a skeptic, and have doubts that, if there ever was an effect, it could still be significant seven years on. I was reminded of it by this, from the BMA's 1992 cycling book (pp41-42), compiled by Mayer Hillman.
Alternatives often only become apparent when they are seen to be a realistic and appropriate option. The foremost instance of changing attitudes to the bicycle which has developed in recent years is in the commercial sector. Firms wanting messages delivered quickly in cities are now using cycle couriers: bicycles have been found to be faster and more reliable than motorized means of transport. During the London rail stoppages of 1989, a significant number of commuters appeared in the streets on bicycles. They were then seen to be an appropriate and acceptable means of travel. Some continued to cycle even after the initial reason for doing so had gone away, as their experience had in some ways modified their attitude. It may be that many more, if provided with good cycling facilities, would have become regular cyclists.