Why are motorists so afraid to turn off their vehicles? I see drivers idling while using their phones, waiting for a bridge lift, etc.—even in nice weather. I would think that it would be more environmentally friendly to turn off your engine. —Stephen K.

There are two main reasons for the phenomenon you're observing, Stephen (excluding the small fraction of people who believe cars are like sentient robots and turning them off is the same as killing them).

The first, obviously, is that people are assholes. When it comes to global warming, no sacrifice is too great, as long as we don't have to make it ourselves. The wrist-numbing tedium of shifting into park, the stifling hell of five minutes without air conditioning, that annoying little gap when the radio shuts off while the car is starting back up—it's all a bit much.

Of course, when making a cravenly selfish decision, it's always nice to have some fig leaf of misinformation with which to justify it. Republicans do this by simply denying there is such a thing as a "planet," but we libtards need a better excuse.

Luckily—and this is reason No. 2—we have the persistent folk belief that restarting a car actually burns more fuel than letting it idle for a few minutes.

There was a time—back when fuel was a nickel a gallon and doctors still recommended pumping your nursery full of exhaust fumes to calm a colicky baby—when this was true. In those days, your engine was carved out of solid pig-iron, and to warm it up you basically had to drizzle the engine compartment with gasoline and throw in a lit cigar.

If you've ever seen an old person pumping the gas pedal as they start a car, that's a holdover from this era. Modern cars are vastly more efficient, and can start using no more fuel than they burn in 10 seconds of idling. So if you're going be stopped for longer than that, turn it off.

Save the date! On Sat., Sept. 7, Dr. Know celebrates 10 years with "That's Edutainment!" a multimedia extravaganza at the Alberta Rose Theatre. Tickets go on sale July 10.