Cruise-control limit?


#1

Why do cruise controls cut off at below about 25 mph? I could use the ability to cruise at as low as 10 mph, but have never seen one that will do it. Can this be changed by reprogramming a computer (2003 Silverado and 2012 Rav4)?


#2

I believe it used to be because of vacuum issue when cc was vacuum operated.

Not being able to engage the cc below 25 I am sure is a safety issue. It would be unsafe to use the cc in slow traffic


#3

At lower speeds modulating speeds is a must for safety. I would be hard pressed to find a place in town you could drive 25 mph for an extended time. Also, plan on a lot of shifting at lower speeds. That completely negates using the cruise on a manual and really puts the auto in the hunting mode. I would think it safer that you move the selector into a lower gear to get some engine braking at say, 25 mph which would make it easier to sustain the speed rather then use the cruise.


#4

There is a reason it’s called “cruise” control. At 25 mph and slower you are not cruising.


#5

It sounds more like a carry-over from pre-computer run cars as the first poster suggested.

Since there never seems to have been an era when it was possible to get cruise-control at speeds below 25mph, there can’t be any “safety issue” except in someone’s imagination.

It wouldn’t bother me to call it a crawl-control instead of a cruise-control.


#6

@NJ Frank, I did not suggest that this is because of precomputer era. What I stated was back when cc was vacuum operated the cc would not engage for lack of vacuum.

Since there never seems to have been an era when it was possible to get cruise-control at speeds below 25mph, there can’t be any “safety issue” except in someone’s imagination.
Respectfully, there is a safety issue here. If cc could be engaged under 25 then would it be safe to cruise in a construction zone, school zone, parking lot, subdivision, rush hour traffic, etc? Even though it would not be safe it would happen if it were available.


#7

Respectfully, there are only 2 places in the state of NJ where cruise control is necessary. Northern sections of 287 and western sections of 80. Otherwise, traffic dictates the speed.


#8

there can’t be any “safety issue” except in someone’s imagination

For as long as I have been involved in product design, there is a process that starts at the moment of conception; hazard and risk mitigation. At that stage it is ALL in someone’s imagination. However, people are pretty good at envisioning risks even if they have no predicate device to base it upon.

It would take all of 30 seconds for a group of people considering risks associated with throttle control to identify this as a significant risk just as some people here have envisioned it.

BTW- You can find articles and reference material that cites the same reasoning.

There are lots of product features you will never see because the potential for harm identified early on in the product development cycle indicated there was a significant risk and there was no way to sufficiently mitigate it. Sometimes, the hazard is identified but allowed to exist because the return outweighs the risk but on something like this, it is a convenience not a necessity, so that makes the decision easy.


#9

It’s a safety issue, 25 mph and below is typically in traffic, CC could easily lead to problems.


#10

Any scenerio I can imagine at speeds of below 25 mph is going to involve regular stopping and/or slowing down. Most people I’ll bet take their foot off the pedal and rest it on the floorboard when using cruise control. I believe it takes longer to apply the brakes from the floor than it does from the accelertator pedal, thus using cruise control at speeds that low wouuld prolong your braking response time in a situation where you need good response time.

I believe it’s a safety issue.


#11

I’ll just have to ramble this answer to all the stuff above:

Just because I’m FROM New Jersey doesn’t mean I’m IN New Jersey. I live in rural Oregon where there are roads you can drive all day without seeing more than a couple of cars or, more likely, pickups.

A cruise control at sub-25 mph is a hell of a lot less dangerous than one at above 25, that kind of reasoning should make it impossible to use it at higher speeds, not lower: braking distances are much shorter at 15mph than at 50 (where I can use CC), so the reaction time argument is nonsense. The town I live in has speed limits of 20 and 25mph: how is it more dangerous for me to use CC in the 20 zones than the 25s?

How is it possible that diving in places that have speed limits below 25 mph at 40 mph, where I could use CC, is safer than driving at 20mph on CC?

All CCs I know of shut off when you touch the brakes. In traffic that makes using it much more inconvenient, maybe enough so that most people wouldn’t use it at all in traffic.

If drivers are allowed to have high-horsepower vehicles easily capable of 100+mph that is an illegal and dangerous speed in all states, why shouldn’t we also be entrusted to go 10mph on CC?

I find your arguments to be specious.


#12

To put it simply, I’m inclined to think it’s more imperative to keep your feet in the pedals around the local neighborhood schools and playgrounds than on a divided limited-access highway.

100 mph is illegal almost everywhere. And on the verge of being out of coontrol in almost all mass-produced vehicles.


#13

NJ Frank, now I’m really confused - you want to set your CC at 25 mph on rural, empty roads? Why?


#14

There’s nothing that says you can’t keep your feet near the pedals. A couple of my cars have cruise controls that still work at 25, and I do use it. I keep my foot over the brake, but set it at 25 because it’s extremely easy to creep up from 25 to 30 without noticing it (since I’m generally watching very carefully in such zones for kids running out in front of me, and don’t want to keep my head in the cockpit, as the pilots say), and then you get a ticket.

I think the real reason that cars don’t have cruise controls that work at lower speeds is because a lower limit has to be set somewhere, and some engineer figured no one would ever intentionally drive that slow for any length of time.


#15

I don’t know for sure where the 25-30 cut off came from. I suspect below 25 if the CC called for more throttle it might overshoot the mark and cause a downshift and result in a too much power and over accelerate for the situation. I’m sure designs for stable control of speeds below 25 is possible. Whether it would be “cost effective” is the question?


#16

That may actually explain it UT - - my older cars have lower limits well above 25mph. My newer ones go at least down to 25 (the lowest I’ve tried to use cruise). And, coincidentally, my newer ones have drive-by-wire throttles and much more advanced induction systems, and are therefore easier for the computer to precisely control.


#17

according to my design doocuments
http://tijil.org/Scion_Docs/Scion_06_misc_docs/2007sciontc_ncf%20Folder/cruiseco.pdf
my lower limit is set at 25 mph


#18

I would like to use my CC at 10 or 15 mph because I’m a wildlife/bird photographer, but I have physical limitations that prevent me from carrying my heavy equipment on foot much anymore, so I shoot from my vehicle window a lot and cruise possible areas for subjects. Also, in most vehicles, my throttle foot gets cramped trying to hold a steady slow speed for any length of time.

So, picture me on a lonely gravel road in a wildlife refuge creeping along with my head swiveling around for subjects that often turn up 20 or 30 feet away and trying to stop before I overshoot them and scare them off. There are days when I don’t see more than a dozen vehicles when I’m doing this.


#19

ok, I understand your scenerio but it is what it is. And that is unsafe at slow speeds. You wont understand this but picture yourself cruising along a gravel road searching for a pic and all of a sudden you are nose down in a ditch not able to back out. All because you were not paying attention because you had the cc on and you were not watching the road. Its hard to watch the road and search for photo ops.

I get you since I to enjoy bird watching but unsafe.


#20

I think Uncle Turbo has it. IMHO its just too low to avoid endless shifting and over shooting and undershooting. But lets go back to before CC was around. Driving all day through Nebraska or someplace, your foot would get very tired. CC allowed you to rest your foot and reposition your leg a little on long trips. I don’t think it was ever designed as a low speed throttle control like on a tractor. I think what you really need is a throttle control where you can set the engine speed. With the electronic throttles now though, its not as easy as a cable like the old days. If you are really serious, I think I would check with someone that outfits cars for handicapped with hand controls etc. They may have a throttle control kit that would come off the set when the brake is hit.