In Back to the Future, why was the speed 88 miles per hour?

• Why not use 89, maybe 100 miles per hour? Is 88 the fastest a DeLorean can go? In other metrics, I have:

``````Miles per hour         88.00    [mph][mi/h]
Miles per second        0.0244  [mps][mi/s]
Yards per second       42.944   [yps][yd/s]
Feet per second       128.832   [fps][ft/s]
Kilometers per hour   141.3648  [km/h][kmh][kph][kmph]
Kilometers per second   0.0393  [km/s]
Meters per second      39.3     [m/s]
Knot                   76.3931  [kn] nautical mile per hour
Mach Speed              0.1155  [Ma] (speed of sound)
Light Speed             1.3110e-7 [c]
``````

There does not appear to be anything special about this number. So why was it 88 MPH?

I'm guessing because the led display would seem more dramatic if all the lights were lit up and since 88 is the number that would do this, it was what was chosen.

Must be for the yards per second metric - I see 42 in there.

@OghmaOsiris - I think you can even take this explanation in-universe. Imagine that the speed is arbitrary - you fix it by changing variables in the machine...Doc has to come up with an arbitrary large speed, and since he's using an LED display for the spedometer, he decides it would look cool. We know that Doc has a flair for the dramatic anyhow.

@ChrisB.Behrens: precisely. Because it’s *cool*.

5280 ft in a mile. 5280/60=88

There's also the fact that you wouldn't normally (unless you're on the Autobahn) travel at 88 Miles Per Hour. So setting it that high seems like a safe bet to avoid accidentally activating the time machine.

@Zibbobz Is that really true in the US? 88 mph or 140 kph is a perfectly common speed to travel on most motorways/highways in most of Europe, which is something I always found rather odd about this.

@JanusBahsJacquet 70 MPH is more common on highways in America because there was originally a national speed limit of 65 MPH on all highways. It's been repealed since 1995, but some states (including mine) still have a 65 mph speed limit. Other states have higher or lower limits, but most aren't any higher than 80, so 88 would be considerably fast (and faster than legal in 1985, when a 55 MPH limit was the national law https://en.wikipedia.org/wiki/National_Maximum_Speed_Law )

The train had to push the DeLorean 88 mph but the speedometer was calibrated for standard tire circumference. On the train tracks, the tires were removed so only the rims were on the tracks, thus the speedometer would move faster given the same velocity, requiring less velocity for time travel when pushed via train. In other words, its not consistent.

The point is that it's 236,544 furlongs per fortnight.

Borrowed from numerology - "The energy represented by the numerology number 88 is, foremost, an analytical approach to efficient business for accomplishing substantial goals."

@JanusBahsJacquet Indeed, 140 km/h is about the speed you end up with after hitting the breaks because a Golf dared to enter the left lane on a German Autobahn ...

• As you can see here the original set of DeLoreans were fitted with speedometers that went up to 85 MpH:

Further evidence on Wikipedia supports this.

The fact it needs to reach 88 MpH may be an indication that the DeLorean is souped up, or that time travel is impossible. Or even just it needs to be turned up to 11 to get time travel.

so many cars of the 1980s had speedometers that only went to 85, that the case for "up to 11" is strong.

That's because in 1979, the NHTSA made a regulation limiting speedometers to 85 MPH (as well as special emphasis on 55, which was the national speed limit at the time).

@JustJeff : :) I can't resist... about the "up to 11": http://xkcd.org/670/

I actually had some doubts. This picture implies that not all Deloreans have the same dash or speedometer: http://www.deloreanowners.org/gallery/IMG_2331.jpg

@Pureferret The 140 mph speedometer was for cars intended to be sold in the UK and Europe; at the time US regulations required that speedometers top out at 85 mph. DMC now has a replacement 140 mph speedometer and metric cluster for sale.

This would be a good in-universe explanation for why Doc's Delorean had an extra digital speedometer mounted on top of the dashboard (out-of-universe, they probably just put it there so the audience could easily see the speed in point-of-view shots looking out the windshield)

To add to my comment above, p. 67 of *We Don't Need Roads: The Making of the Back to the Future Trilogy* notes that a 1979 law set by the National Highway Traffic Safety Administration required that all speedometers have a maximum speed of 85 mph to encourage safer driving, and that although it was repealed 2 years later, production of DMC-12s ended before the repeal so they all had that limit. So, special effect supervisor Kevin Pike "not only replaced the manufacturer's speedometer with one that went beyond the regulated amount, but added a digital display for additional good measure."

Luckily, I could smell the TVtropes link from a mile away so I managed to avoid clicking on it. The day is saved! :)