Perhaps weather wasn't in the program, but one should always use judgment with computer mapping. For example, I have used DeLorme Street Atlas for many years and it has worked very well. But on two occasions its "fastest" route, as based on its knowledge of distance and its idea of maintainable average speeds, led me astray. Once was simply a route through an urban area in Connecticut where the shortest route had a million stoplights, or maybe two million. The other time was when its idea of a shorter route around a small town in Vermont turned into a steep dirt road. It was actually dangerous because part of a steep section was quite muddy from rain runoff. In both cases I could have concluded what might happen but foolishly didn't.

Some friends once followed a computer's route from Burlington, VT to Alburg by going through the towns on the little islands that populate the northern end of Lake Champlain. If they'd looked at the map the would have seen how the computer somehow missed I-87 that could have shortened their trip by over an hour.