The experiment is messed up. Business and rental drivers are usually much more careful in their driving patterns because the car isn't theirs. They are usually adults, experienced drivers who don't put themselves into risky driving situations. = Speeding, cutting off others etc.. It also didn't tell how much the cars were driven. There may have been a down turn in the economy and thus less business driving and same with the rentals. If they were used less after the installation then the study wasn't really valid. What was the price of gas before and after the instillation. Who did the study? Did the previous testers have any reason to skew the study? Did they own stock in the third light business? Was it the same people who did the study before who did the study afterwords? What was the average age of the drivers before and after? The study group may have aged and calmed down a bit more? What were the technology changes that occurred about the same time? Anti skid brakes, better material and tread designs for the tires, what about the design of the gages and their lighting. How about the window styles and size..larger windows mean better view and potentially less accidents. What were the safety aspects of the cars before compared to the cars after, were they the same makes and Models or did the rental and business learn that certain cars were safer than others and move to the safer Models? so many variables to consider but did the tester consider them all-probably not. Random studies study only a certain percentage of the total. Who's to say the second random study didn't get less experienced drivers to study? All good what ifs'.