In this Wednesday, Nov. 6, 2013 photo provided by the Tennessee Highway Patrol, emergency workers respond to a fire on a Tesla Model S electric car in Smyrna, Tenn. Spokeswoman Liz Jarvis Shean says Tesla has sent a team to Tennessee to investigate the fire. Two other Model S cars have caught fire in the past five weeks, one near Seattle and the other in Mexico. (AP Photo/Tennessee Highway Patrol)

The recent timing of events has been off for Tesla Motors. Three fires in three Model S EVs within six weeks looks pretty bad. But how do these separate events stack up against all the other cars on American roads?

Observers are waiting to hear what started the Tennessee CarBQ on November 6, but there's been a wave of concern over the safety of the Model S after this event (and the previous fires in Mexico and near Seattle). The company's stock has been hit hard as investors worry but the people behind the electronic wheels are not fretting as hard. For the driver in Tennessee that day, Juris Shibayama, example, safety wasn't enough of a concern to stop him from driving his next Model S.

Automotive News editor Dave Guilford did a "little back-of-the-envelope math" to put the latest Tesla fire into perspective. The state of the battery chemistry and vehicle structure should be left to experts to figure out and Wall Street will determine the stock's value, he said. For now, we can calculate that, since Telsa Motors stated that it has "over 19,000" Model S owners in its third-quarter earnings letter, if you divide that number by the three fires, that comes out to one fire per 6,333 Model S units that have been delivered to owners.

If you compare that to the number of car fires on American roads, it puts things into perspective. The US Department of Transportation reported that there were 253,108,389 registered vehicles on US roads in 2011 (yes, that it is a lot – nearly one per person in the US). The National Fire Protection Association says that there were about 187,500 car fires in 2011, and that 270 people died from it. That ratio comes out to one fire per 1,350 vehicles on the roads that year – much higher than what the Model S has experienced.

Perhaps the comparison is a bit rough on the edges. Most all of these passenger vehicles have internal combustion engines, and many of them are dilapidated older cars, some up to 20 years old. It would be more accurate to calculate the number of fires per miles driven, but that data isn't available. Fires in Tesla's electric vehicles are much less commonplace than in vehicles powered by gasoline and diesel, Guilford says. We would make two other distinctions: none of the Model S drivers have been killed or injured from the fires, and they're interested in owning another one.