Something that’s always bothered me about driving is I can drive 5 mph over and barely speed up the gps, however if I accidentally drive 5 under the speed limit, (My brand new truck doesn’t have a speeding) it will add a bunch of extra time. Is there an equation or something that shows you how fast you’d have to go to actually lower the time needed to arrive. Is it just a mental thing or is it math. Any and all information welcome!
In: Mathematics
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Many modern driving apps don’t use speed limits to calculate your ETA. Rather, they use the current speed of other users driving on the roads you are routed on.
Since most drivers are going 5-10 over the posted limit, driving even the actual speed limit will often take longer than the apps calculated times.
Say you are going 60 mph and travelling somewhere 60 miles away, it will take 1 hour.
If you are going 65 mph it will take 55.38 minutes.
If you are going 55 mph it will take 65.45 minutes.
So speeding up by 5mph saves you 3.62 minutes, but slowing down by 5 costs you 5.45 minutes.
Intuitively this makes sense if something takes an hour, if you go half the speed (50% slower) it will take twice as long in the example above two hours, but in order for you to save an hour you would need to arrive instantly (infinite mph). Idk beyond that it’s just how math works.
Because speed and time to destination are not linearly correlated. Reducing your speed by a certain amount to travel a set distance will always increase the time taken by more than increasing your speed by that same amount would lower it.
Traveling to a place 5 miles away at 50 mph? It takes 6 minutes. At 55 mph, it takes 5 minutes and 37 seconds. At 45 mph, it takes 6 minutes and 40 seconds. Not a large difference, but you can see how it works.
For a more extreme example: imagine you are driving 5 mph, to a place 5 miles away. It takes you one hour to get there. Go 10 mph, and it takes you half an hour. Go 0 mph, and you *never arrive.*
Let’s say you’re driving 100 miles if you drive at 105 mph you’ll arrive in 57 min
If you drive 95 mph it will be 63 min
That’s a 10% slower result.
Maybe that helps. Not sure if it does. In my life I’d rather just take it easy and get there 6 min slower.
5 MPH faster decreases the time less than 5 MPH slower increases it, but only marginally. As allowable speed increases, the amount of time saved by speeding 5 MPH over decreases. There is an equation to show the relationship between time saved and allowable speed. Know this, if the limit is 60 MPH and you go 70 MPH you will save only 1 minute over a distance of 12 miles.
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