MythBusters Test Right Turn Efficiency
I’m a sucker for science, testing, and of course the MythBusters. On last night’s episode they tested the “right turn myth”– basically the way they framed the myth was to determine if it is more efficient to make three right turns rather than to make one left turn. Having discussed this issue several times in the past I was curious to see how they performed the test, their results, and to see if I would agree with their overall process.
The myth was setup from the perspective of a delivery truck driver. Several locations within the San Francisco area were setup as delivery points, then two routes were derived. The first route was a more “logical” route trying not to favor right turns. This route had eight left turns, four right turns, and a total distance of 5.2 miles. The second route tried to exclude as many left turns as practical. The “right turn” route was 6.8 miles long, had one left turn and twenty-three right turns. Each route visited each stop in the same order.
The MythBusters concluded that right turns were indeed more efficient in their test. While the route favoring right turns was a longer distance and took a longer amount of time, it used only 4.0 gallons of fuel compared to 6.8 gallons of fuel on the “control” route. But I don’t think this tells the whole story…
The route they picked doesn’t really follow the premise of the myth as I understand it. For example the order of the stops was the same for both routes. This seems unnatural. While there are different levels of delivery services that demand different delivery times the order of the stops meeting those delivery times doesn’t necessarily matter. Software to construct the most efficient route could likely create an even more efficient route still favoring right turns but also allowing for strategic ordering of the stops. While I agree with their conclusion… right turns are often more efficient… the results might be even more dramatic than highlighted in their route.
Another factor they didn’t consider was labor. Saving fuel does cut costs, but what about the fact that the delivery companies are paying not only for fuel, but also the salary of the driver? This is especially important as the route favoring right turns had a 17% increase in the amount of time needed to drive the route.
I dug around a little bit and found a few references to wages of delivery drivers. While it does seem to vary quite a bit, most references seemed to point to a wage of around $28/hour. The route with more left turns would result in a labor cost of about $24.27 while the route with more right turns would result in a labor cost of about $28.47 Advantage left.
Now that we are considering labor costs, let’s also consider fuel costs rather than just the amount of fuel. According to GasBuddy today’s average gas price in San Francisco is $3.12 per gallon. Using the figures provided for fuel usage on both routes, the fuel cost for the first route would be $3.54 while the route favoring right turns would cost only $2.08. Advantage right.
When considering both fuel costs and labor costs, I’d calculate the route with more left turns as costing $27.80 while the route favoring right turns as having an overall cost of $30.55. Using these figures, the total cost of the route favoring right turns cost 10% more than the more natural route which had more left turns.
While I disagree with the way the myth was tested and my calculation of overall costs would dispute the myth that right turns are more efficient, I still agree with the premise that when practical, right turns should be favored over left turns. (Assuming your country drives on the right, as an astute Twitter follower pointed out.) When turning right you generally just need to wait for traffic coming from the left. When turning left you need to completely cross one lane of traffic after waiting for traffic from both the left and right. Similarly many jurisdictions allow “right on red after stop” so even if you have a light you might not need to wait. While there is no such allowance for the light while turning left.
The question should be asked like this. When building a route should you allow longer wait times for left turns or right turns? The answer of course is that turning right will generally be faster, therefore building routes that reasonably favor right turns will be more efficient.
I’m reminded of the phrase “two wrongs don’t make a right, but three rights make a left”.