Transportation infrastructure significantly contributes to a nation’s prosperity by facilitating workers’ access to employers, consumers’ access to shopping and leisure activities, and firms’ access to capital, labour and potential customers. The public sector has generally provided the vast amount of a nation’s infrastructure – roadways, waterways, railways and airways – and expanded it to satisfy users’ growing demand for transportation. But as demand has increased and ageing infrastructure facilities have required ever-greater funds for maintenance and new construction, capacity has become increasingly strained and travellers and shippers have experienced more congestion and delays. Policymakers have tried to find new sources of money to finance projects to expand capacity; but congestion and delays have persisted.