Social Question

Kraigmo's avatar

Some people have no idea that they should speed their car up prior to an incline (a hill). If this is you, will you explain yourself?

Asked by Kraigmo (8562points) April 19th, 2021
34 responses
“Great Question” (0points)

Your car has to work many times harder to go up a hill if you fail to speed up prior to the hill.
How could any adult not figure this out?
If you haven’t figured this out, please explain why. How can you go years…. or decades…. without observing natural physics?

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zenvelo's avatar

If I am already driving at the speed limit, it isn’t legal to “speed up” on the flat before a hill.

The car has an accelerator and gearing, when I start to climb I step on the gas and the transmission senses the load and downshifts. None to break the law.

Kraigmo's avatar

So to avoid a technical “law” that no Highway Patrol would ever enforce…. you are willing to go hard on your car and cause dangerous bunch-ups behind you?

JLeslie's avatar

They didn’t go to driving school maybe?

Grew up in a place that is very flat?

Those are my guesses. I was taught to accelerate a little before an incline. I always wondered if cruise control works the engine harder in very hilly places.

doyendroll's avatar

Was it all uphill from then on when someone was away the day they handed out physics.

hello321's avatar

You should never speed up prior to an incline.

zenvelo's avatar

@Kraigmo I have been driving hills and mountains for fifty years. I know what I am doing and I don’t cause back ups unless I am in an overloaded vehicle, in which case I am in the slow lane anyway.

I drove both directions over the Grapevine between Bakersfield and Los Angeles just a few weeks ago. Any momentum built up on the approach to the hill is lost in about fifty yards; and then you still need to have your foot on the accelerator to maintain speed.

Accelerating from 65 to 80 while approaching a hill so that one can cruise up the hill at 65 is foolish and doesn’t save any wear and tear on the engine.

kritiper's avatar

I think too many people are too concerned about what is going on inside the car to worry about what’s going on up the road.

kritiper's avatar

The car’s Cruise Control works like a speed governor. If the vehicle starts to slow down while climbing a hill, the governor increases throttle to compensate. The opposite is true if the vehicle starts to go down hill.

JLeslie's avatar

I’m really surprised by many of these responses.

Just curious, the people saying not to accelerate, did you take driving class? It’s just a couple of mph more for a few seconds. I don’t mean that as a put down, I’m generally interested if you took class and it wasn’t taught to you.

“Initially, you want to gain some speed while approaching a steep incline. Extra speed will help push your car up the hill and make it easier for it to maintain acceleration.”


Other hill-driving things that were taught to me are to ease up on the gas as you approach the top/crest to be ready to brake, because you can’t see over the top of the hill.

To be able to see the wheels of the car in front of you when stopped, ESPECIALLY when stopped on a hill, because the car in front might roll back, something most Americans are completely clueless about. Luckily, newer manual cars have a stop that helps prevent the car from rolling back. It also gives you room even on flat ground to get around the car in front of you if the car for some reason isn’t moving when it should.

Dutchess_III's avatar

No I don’t. I have the preternatural ability to maintain my speed while going up the incline. Same with going down. Crazy, I know.

hello321's avatar

^ This. You just pay attention and keep the same speed.

ragingloli's avatar

Well, I take the Bus and the Train, so it certainly is not me.

zenvelo's avatar

@JLeslie Hills in California are a lot different from those in Florida. But your statement and @Kraigmo‘s statement to ”... speed up prior to the hill” don’t really do anything unless you speed up a block or two (one hundred yards?) before a hill. And the dangers from doing that on city streets is downright dangerous.

And on a freeway, one can’t go fast enough prior to a hill to gain enough momentum so you don’t have to stomp on the gas anyway.

My question for you: did you take driver’s ed in a place with hills? I learned to drive here

JLeslie's avatar

@zenvelo Yes, I did learn to drive in a place with hills. I lived in Maryland. I’m not thinking city streets so much. I take that to mean lots of traffic lights. More in my mind was maintaining constant speed during highway-like driving. I say “hwy-like” because even rural roads with no lights would be similar. Even in the city I would usually exercise slight acceleration before going up a hill, but there are many many factors in city driving that I might not.

On a highway you are basically going a block every 3 seconds, assuming 20 blocks in a mile. You can begin to push on the gas a few seconds before the incline.

So, are you saying you did take Drivers Ed? Or, just that you lived in a place with hills. Or, maybe the disagreement in this Q has more to do with city driving vs highway and rural.

Edit: as a side note I hope 16 year olds learning to drive in mostly flat Florida are taught how to maintain speed on a hill going both up and down.

zenvelo's avatar

@JLeslie I took Driver’s Ed in high school, as did most kids in the early 1970s. And I learned on hills, including in San Francisco.

Check out Fillmore Street between Green and Broadway in San Francisco. The hill is so steep the sidewalk has stairs. But going up the hill, one accelerates as one enters the intersection from a stop, but one is barely up to 25 mph when the incline begins again. You don’t get to speed up ahead of the hill.

JLeslie's avatar

Not having the opportunity to speed up is completely different.

hello321's avatar

^ Why do you think you should speed up prior to going up an incline? I’ve never done this, and keep a consistent speed across every incline.

I don’t believe driver’s ed teaches this in MA. I also know that you’ll get ticketed in MA, NH, and VT if you try to use a hill as an excuse for breaking the speed limit.

So, there is zero reason to do this. This is very confusing.

Brian1946's avatar


“I have been driving hills and mountains for fifty years.”

Having occasionally driven the SF Bay area hills with a stick shift from 1967–1979, I thoroughly respect your perspective.

Have you ever driven up the Sherwin or Tioga Pass grades?

Perhaps you’ve even driven the I70 from Denver to the Eisenhower Tunnel.

kritiper's avatar

I don’t think “Speeding up just before a hill” means hitting passing gear and topping out at 120 MPH. Giving it a little more gas right at the bottom is just right. But, then, I think you would do it naturally.
And the engine isn’t going to work any harder. If you have a automatic transmission, the vacuum modulator (or throttle valve or computer system sensor) will sense the drop in engine vacuum and downshift the transmission if the transmission governor (or computer system speed sensor) tells it that the car is moving too slow for that gear.
If you have a manual transmission, you will know that the gear you’re in can’t hold the speed on the hill and you will downshift.

JLeslie's avatar

@hello321 Momentum, velocity, gravity. If you take a ball and push it harder at the bottom of a hill it will travel farther up the hill.

If you want to push the gas when you’re already on the hill go ahead. I would think it’s easy to lose speed doing that, but if you time it perfectly you probably don’t. That’s fine, do it how you want, it’s not a big deal. That’s what cruise control does.

It’s like slowing a little before a curve, so you can accelerate into the curve. Do you do that?

zenvelo's avatar

@Brian1946 I have driven I 70 in both directions many times, as well as Tioga Pass from both sides. Also Independence Pass in both directions. And I stand by my statement that “speeding up” to carry momentum is a waste of time, when one just steps on the gas as you go up the hill.

The momentum dissipates almost immediately unless you step on the gas. And then your engine labors the same as if one started from a stop on the hill.

hello321's avatar

@JLeslie: “If you want to push the gas when you’re already on the hill go ahead. I would think it’s easy to lose speed doing that”

It’s never happened.

This might be the strangest thread on Fluther in a long time. I have gone through life assuming people have the ability to accelerate or decelerate when driving, only to learn that they’re just relying on gravity to get them where they want to go.

Are we sure we’re talking about motor vehicles and not bicycles?

kritiper's avatar

@JLeslie The proper way to pass through a curve is to slow ½ way through and accelerate coming out the other ½. (Learned that on Adam-12.)

JLeslie's avatar

@kritiper I’ll ask my husband. He so often takes a curve at full speed and it makes me a little sick to my stomach. Between g-force, and my anxiety about getting into an accident, I hate the feeling. Only on some curves of course, it really depends on the situation.

Brian1946's avatar


Is there something about the phrase, “thoroughly respect your perspective”, that caused you to think I was disagreeing with you?

I’m well aware of the effects of gravitational deceleration on going uphill.
I only mentioned those drives because I think they’re spectacular.
Actually, they’re major examples of how little benefit there would be in speeding upon approaching a hill, or those cases, the tallest mountains in the lower 48.

Since the 120 ends at the 395, and is apparently perpendicular to it at that T-section, both the northbound and southbound entrances to the 120 involve sharp turns.
So the only acceleration I remember going up the 120 was approaching the speed limit.
BTW, do you remember what the speed limit is on that part of the 120?
IIRC, it’s 45 before before you hit the curves, and 30 on them, but I haven’t taken the uphill route since 1979, and I haven’t taken the downhill since 1994.

Another drive I love is the one going up to Lake Tahoe from the 395.

zenvelo's avatar

@Brian1946 I wasn’t quite sure.

Driving Independence Pass (12,095 ft altitude) in Colorado, there are hairpin turns at the start of teh climb in each direction; one has to slow to under15 mph.

And yes, I remember the T intersection of 120 and 395 in Lee Vining. Turning onto 120 and seeing a wall of mountain ahead.

Brian1946's avatar


Wow, 12,095 ft. The highest I’ve ever driven is the Ike Tunnel, which I think is 11K.
I’m sure the view from the Pass is way better than the one in the tunnel. ;-)

dabbler's avatar

“Your car has to work many times harder to go up a hill if you fail to speed up prior to the hill.”
Citation needed, please explain.

To reach the top of the hill, the mass of the car has to be lifted from the bottom of the hill to the top. In what case does the amount of work done change because the starting speed is different?
If you include the energy (wasted) to get your car going faster than it was (increased wind drag etc) in what way is any energy saved to get the car to the top of the hill?

One way or another the amount of work to move the car from bottom to top will be the same.

hello321's avatar

I’m still puzzled by this question. It makes zero sense why anyone would need to speed up prior to an incline in order to maintain speed on the incline.

crazyguy's avatar

My Tesla can handle any hill without the need to speed up ahead of the hill. We have a hill in Laguna Beach that is on Third Street which is at least 25 degrees. It has a stop sign just ahead of the hill. So speeding up is not possible. I have seen drivers so scared of it that they will use alternative routes. Not I.

Kraigmo's avatar

@hello321 Because Forward Momentum is virtually free gas in the moment; And also for safety. When an interstate freeway has a stretch of hills that go up and down several times, you always see traffic jams in the valleys of those declines. That’s because one or more people were going way too slow. It’s very dangerous. The only reason one should go slow, is if there’s a person in front of them going slow, or a corner coming up that less than 5 seconds away.
Cars shouldn’t be bunched up in wolfpacks on the freeway. But they are. Because too many slowminded people are blocking the natural flow of everything. If they got out of the way or sped up, everyone could fan out, and the freeway would be way safer and way more efficient.

Dutchess_III's avatar

It’s not forward momentum. It’s upward momentum, which drags on the car @Kraigmo. (Good to see you!)

dabbler's avatar

Rampant misunderstandings of physics and safety on display in this thread suggest that we need self-driving cars ASAP.

Forward Momentum isn’t free at all. You paid for that with a heavy foot earlier. And because you’re going faster than you would have been you suffered more aero drag.
It won’t cost you any more gas to pull up the hill at a safe speed than it cost gas to ‘bank’ that momentum ahead of the hill.

“Wolfpacks” happen because some drivers know how to regulate their speed, and apparently some don’t. There’s no reason in a modern car not to maintain a consistent speed up and down hills.

Dutchess_III's avatar

Wolf packs happen too, because some people are afraid to think for themselves so they just do what the person in front of them is doing.

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