We live in uncertain times and present trends seem to lead to a gloomy future. The promotion of walking as a transport mode is described here as an essential element of policies aimed at avoiding increased social inequalities, poorer life quality, economic slump, deteriorating health and rising violence, which could all be the consequences of higher petrol prices in anticipation of a final oil shortage. What we now know of global warming similarly leads to considering that walking and, more generally, non-motorised transport modes will have to grow. The optimistic vision is that reducing the dependency on oil of the transport system by developing new forms of mobility through combining non-motorised and collective modes can be made desirable through adequate policies. The pessimistic vision or "doom scenario" is what will happen if such policies do not develop. The policy-areas involved include urban planning and design, transport planning and operations, work organisation, access to services. Such policies will involve public and private stakeholders. They will have a cost for the tax payer, but doing nothing may cost even more. A most important point is that working on such policies should start now as the time-schedule for the unwanted changes promised by the current trends are to be expected in the short-term.