Heavy Traffic

The worst part about traffic congestion is not the stop-and-go, delays, or wasted gas, but the unpredictability of it all. If you need to be somewhere at a certain time, you don't know how long your trip will take, forcing you to add extra travel time to your schedule.

That's called Planning Time as opposed to Travel Time, according to Texas A & M Transportation Institute's 2012 Annual Urban Mobility Report. The Transportation Institute has not only named this annoyance, but also measures it using the Planning Time Index or PTI. If your trip has a PTI of 3.00, that means you have to schedule 60 minutes for a trip that would take 20 minutes in light traffic if you want a 95 percent chance of getting there on time.

Average PTI varies by size of metropolitan area from a high of 4.08 in metro areas with populations of 3 million or more to 2.09 in metros with fewer than 500,000 residents. The most unpredictable commute is in Washington, D.C., which has a PTI of 5.72. In other words, when traveling the freeways around Washington, D.C., you have to multiply the estimated commute time in light traffic by six (!) to have a 95 percent chance of getting to your scheduled appointment on time.