The transportation sector can learn a lot from the demand-side management experience of the electricity industry. The lesson is that energy conservation (i.e., working to manage demand for electricity) is often the cheapest, easiest, and most sustainable way to provide service to customers. If a customer need light, it's better to provide energy-conserving light bulbs than to build a new power plant.

Similarly, we can design communities that provide greater access to opportunities with less transportation demand. Here's how to think about the contrast between demand-side and supply-side transportation:

Demand-side transportation

• Transportation (mobility) is a means, not an end in itself. 
• What people want is access. 
• Access is better provided by proximity. 
• Transportation is costly, a sign of inefficient land use. 
• Plan land use to reduce the need for transportation. 
• The less transportation the better!

Supply-side transportation 

• Sprawling land uses generate lots of trips by car. 
• The cure for traffic congestion is building more roads. 
• More roads induce more driving. 
• More driving produces more user fees (gas taxes, license fees, tolls) to build more roads.
• New roads fill up with more congestion.