does anybody know what the estimated driving times are based on when you get driving directions from google maps? Yesterday just for fun I googled the directions from my college apartment to my parents house. The estimated time for the route it gave me was 42 minutes, which seemed about right for that route, but that isn't the way I normally go. When I modified the route to match the roads I actually drive, it gave an estimated time of 1 hour, 5 minutes, when in reality it only takes me half an hour in normal road conditions going the speed limit when I go this way. I was just wondering if anyone knows why there would be such a large discrepancy between the estimate and the actual time it takes or why the estimate for the suggested route is more accurate.

Most trips are shorter, timewise, than that found on the directions.

It's an average driving time, figuring in frequent stops for gasoline, to eat, rest areas where you can get out and stretch your legs.

They probably factor in stopping every couple of hours.

When I go on a trip, I'm on a mission.  Stop when I'm low on fuel.  Do drive throughs for most meals, especially breakfast.  Couple of sausage McMuffins with egg and a medium OJ, and I'm back on the road.

I've driven the entire stretch of I-81, from PA to Tennessee w/o a stop.

Not many people like those banzai runs.

I set the cruise at just less that five mph over the limit.  Where the speed limit is 70, the cruise is set at about 74.

If the traffic is buzzing by me, I'll go with the flow.  In light traffic, with no other vehicles to run interference, I don't get greedy.  Been by plenty of state cops, highway patrol, etc, with their radars working.  Never been stopped.

I've heard they won't stop you unless you're exceeding the speed limit by at least 10 mph.

Four to five over is fast enough for me. 

I can't specifically answer your question, but can give you my experience. 

Google says it takes 3 hours and 56 minutes to get to my girlfriends house.  Even in semi heavy commuting traffic plus a gas/bathroom/eat break I got there in 3 hours 35 minutes.  60% of the travel was going to speed limit or less. 

Coming home at midnight I made it back to my place with zero traffic and going 5-10MPH over the speed limit in 3 hours.

I simply use it as a "approximate" time and NEVER as an exact time

I'm always a little faster than the approximate time, but heres a trip im not sure I could make on time. My neighborhood to Oahu, Hawai'i. Check number 42. I guess I need a kayak now 

I travel a lot and have found that Virtual Earth is much more accurate with its driving time predictions.

A bit off topic, but at last year's road trip we went into town to eat.  One of the cars that left the lodge at the same time showed up 15 minutes after the rest of us; the drive was 7-8 miles.  When I asked where they were, they said they followed the directions/route that they downloaded to their phone.  When they showed me the route that got laid out for them I just shook my head,  We had one right and 2 left turns to the restaurant.  They had at least 10. 

They have a lot of factors added in... stop lights and signs, a typical heavy traffic area and so on. Sometimes for city driving it tries to route outside of heavy traffic zones which it thinks is faster, which may only be true during rush hour.

Otherwise the Google map directions tend to be within 5-10% depending on how fast I drive.

I also have compared a few trips with my Garmin GPS using "shortest distance" and "fastest time" settings, Google almost always matched the "shortest distance" which tends to not be faster a majority of the time due to speed limits and stop signs and so on.