What is the speed of a car travel when the brake is not applied?

a) depends on how fast it was going when the brakes were lifted

b) depends on if going up or down a hill

c) depend on if gearshift is in neutral or drive.

Impossible to say with the information provided.

@elbanditoroso From a stopped car. On a flat road. In drive.

I drive a standard. Zero

Given your conditions, I’d guess 0 mph, but some cars may start moving and get up to 1 mph.

Is engine on?
Is the wind blowing? What speed and which direction?
What is the temperature and barometric pressure.
Raining, snowing, sunny?

@gondwanalon Yes. No. No. Normal. Sunny.

The answer is: It depends. Some cars have a drive train that is set strong enough to pull the car along from a dead stop on flat ground. That is how the rear-end accident at stop lights frequently occurs. Someone takes their foot off the brake without paying attention and they roll into the vehicle in front of them. Some cars, given the same conditions would just sit there. There isn’t a given speed…they are not calibrated that way and there are too many other variables.

There was an odd place in Kirtland Ohio that we always called Gravity Hill. It was an optical illusion. It appeared to be an uphill incline, but was really a downhill incline. If you started at one intersection in Kirtland (on King Memorial Road, I believe), stopped the car completely and then put it into neutral, it would pick up speed. My brother and I did it one time to see how far we would go. We made it about 5 miles or so, hitting speeds of about 35 mph (56 kph) in some places. That is slightly different from what you were asking as we were in neutral, but the idea is the same. The only difference is that idling in gear would have given us a nudge at the beginning. If it really was up hill, I doubt the car would have rolled even idling in gear.

Back in my previous life when I was involved in engine controls and calibrations we set the idle rpm to be about 700 rpm which would result in a creep speed of 6–8 mph on level ground.
The rpm would increase if there was an engine load on like A/C, or rear window defrost. The speed could increase to 10mph.
We picked the speed such that all vehicles with automatic transmissions would creep forward from the internal friction of the torque converter. That improved driveability and feel when accelerating from a stop.
Too high a speed wasted gas, brakes, and torque converter life. Too low and the drivers could feel driveline bump when accelerating which put extra load on the differentials and driveshaft u joints. .

@gondwanalon AND WHERE IS THE SWALLOW FROM??? And is it laden?

@LuckyGuy….whut?

Yup @luckyGuy my vehicles would both creep at 6 to 10 miles per hour. I tried this morning on one of them.

@Tropical_Willie Yep. Every manufacturer has their own desired creep speed but in general those are the numbers.
The speeds I quoted above are for a car that is completely warmed up. If the car is in a cold climate and the engine is cold started, you can get up to 12–15mph during the first 90 seconds.

@LuckyGuy

My car idles at about 1,000 RPM when it’s warming up.

How about yours?

@Brian1946 That is pretty typical. On small displacement 4 cyl. engines it can be as high as 1200 to 1500.
I’ll check my Subie tomorrow and let you know.