Adjustable Speed Limiter

98

Now Implemented!

Description

Offer a speed limiter where the maximum speed is set and you can press on the accelerator and it cannot go above that speed.

Competitive/Pricing/Notes

Although Tesla used the same stalk for cruise control as Mercedes, for some reason they only implemented half of it. The Mercedes cruise control can also be switched to speed limiter mode which sets a maximum speed rather than a minimum, actually providing a much easier to use (and safer) alternative to classic cruise control. It’s the one feature I would hate to give up when switching to a Tesla. Especially when driving faster than average traffic, using the limiter is much easier than constantly switching cruise control off/on whenever you have to slow down for traffic.

While cruising at a constant speed, the only difference between CC and limiter is the position of your foot. On cruise control, you tuck your foot somewhere away from the pedals (not exactly ideal for reaction time). On the limiter, you keep your foot resting on the accelerator (which is not fatiguing since you don’t have to modulate it, the weight of your foot is sufficient). In both cases the car behaves exactly the same: it simply modulates engine power to maintain the set speed.

The big difference is when you need to slow down for traffic.

On the limiter, you just ease your foot off the accelerator pedal to let the car slow down at whatever rate you choose, anticipating as much as you like. You then just follow traffic by modulating the accelerator as you normally would. When the road clears again, you press the pedal down to accelerate as smoothly or quickly as you like. As soon as you approach cruising speed again, the car smoothly reduces the acceleration and maintains the set speed (which you can always override, obviously). No need to switch anything off/on, no need to touch the stalk, real one-pedal driving.

Compare this to cruise control: when there’s traffic, you either toggle the stalk several times to select some lower speed (which you then have to frequently adjust again as the traffic does not maintain a constant speed), or switch it off entirely. The deceleration rate is whatever the engineers chose for you and is relatively abrupt on most cars (I haven’t tried in a Tesla). Afterward, when the road clears, you want to get back to cruising speed so you either hit the stalk several times again or hit “resume”. The car now abruptly accelerates, again at whatever rate the engineers happen to have chosen for you until you reach cruising speed. One pedal driving? No, one foot going on and off the pedal plus lots of left-hand toggling and an uncomfortable experience for passengers.

On the limiter, I can drive hundreds of miles in and out of traffic without hitting any levers or touching the brake. With cruise control, you’re constantly adjusting it or switching it off and on. I was recently forced to use classic cruise control and the constant toggling drove me nuts.

There are also a few safety issues where the limiter is, in my opinion, safer than cruise control:

1. Since you have to switch off cruise control when slowing down for traffic (or constantly modulate the speed up/down), you may end up distractedly following that traffic even as it slowly accelerates above your normal cruising speed without you noticing it. This way, I have actually ended up driving 180 km/h instead of my normal 160 km/h cruising speed (which is already well above the legal limit). 160 is just a fine (I like to call it a speed tax), but 180 is an immediate driver’s license revocation in my country. With the limiter engaged, there’s no such risk. You keep following the car in front in a natural way until it gets too fast, at which point the limiter automatically keeps you from absentmindedly speeding more than you intended.

2. Switching off the cruise control or selecting a lower speed is a deliberate action with a slightly higher psychological threshold than simply easing your foot off the accelerator. When driving a car with cruise control, I often find myself going faster than I should in certain situations (cars in front doing funny things, bends in the road) because one tends to hesitate a bit before switching off CC or hitting the brakes. When cruising on the limiter, it’s much more natural to just ease off on the pedal a little bit and gently slow down. Then, when everything is safe again, you smoothly accelerate without ever having had to hit a switch or move your foot to a different pedal. Whenever something on the road makes me uncomfortable, I often notice that I had already slowed down without realizing it. Not so on cruise control, where I would still have been cruising at the same speed. This is probably the reason why we even have road signs warning people to switch off CC when approaching road works.

On Mercedes cars, the tip of the stalk is used to switch between cruise control and limiter. The yellow light next to “LIM” comes on when the limiter has been selected. Tesla has assigned a different function to the tip and the light and removed the letters “LIM” (even though they are still displayed in the photo in the manual last time I checked, and probably present in early models), so I would suggest adding the option to the touchscreen instead. Just an extra toggle switch in the menu: “Cruise Control” / “Speed limiter”. This should be a simple software update.

Status

Implemented with 2018.24.1 software in September 2018.  You can set the speed limit down to as low as 20 mph.  In addition, you can set this via the Tesla app remotely.

(voting combined from a close duplicate that has been removed)

lightly edited by moderator
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     Created 22-Jul-2014

19 Comments

How could you "react wrong"? When the speed limiter is on, it just keeps you from absentmindedly going faster than you intended. When you release the accelerator, the car slows down. When you brake, the car brakes. When you accelerate again, it again keeps you from going over your set limit (unless you override it by flooring the accelerator or turning the limiter off). It's really intuitive.
    Created 25-Oct-2019
I'm apprehensive that an aging driver like myself who's accustomed to CC and never tried a speed limiter, might react wrong when initiating braking or passing when switching between the two different systems. But I wanna try.

To enable CC, while driving press down all the way on the shift stalk. How about enabling speed limiter by bumping it up all the way, disabling cruise?
    Created 25-Oct-2019
A Speed Limiter like MB, Jaguar, Mazda and more have implemented would be of tremendous help when the radar aperture on the car gets blocked with snow, and should be used in those conditions anyway.
    Created 2-Nov-2016
Have it and had it on all of my BMW's, and I'm really missing it on my 'S'

This function can be combined (and improved regarding to the one from Mercedes, BMW and others) with the feature request from another post for an auto speed limit based on GPS location.

The comments in that other post regarding safety issues when overtaking a truck, are not taking into account that you can always overrule the limit, simply by making a cickdown of the accelerator pedal.
    Created 6-Oct-2016
Anyone who has had a car with Speed Limiter, knows that there are NO downsides. All it does is limit your top speed. You still have to drive the car, you still have to accelerate and decelerate, braking does not switch it off (unlike CC). If you want, or need, to go faster, flooring the pedal achieves it. It allows you to accelerate safe in the knowledge that you are NEVER going to break the speed limit, get caught by sneaky mobile speed traps, and can enjoy all the excitement of driving. AND, at the end of the day, it is NOT compulsory. If you don't want to use, you don't have to select it.
    Created 29-Jan-2016
That's quite true, indeed. TACC will slow down for traffic ahead, but not for the drunk swerving in the right lane, the cars on the entry ramp that want to get in, the tight bend up ahead, the stretch of bad road with puddles you know is up ahead, etcetera. A speed limiter allows you to regulate your speed and really adapt it to the situation, while letting you effortlessly cruise at your chosen speed when the road is clear. And most importantly, going back and forth between cruising and slower stretches without having to hit a single button or the brake pedal.
    Created 30-Dec-2015
There is no doubt that TACC is a very smart bit of kit. The downside, for me, is that when there is no car in front, it accelerates to the set speed. On a country road, say 40mph or even 50 mph, it might be legal to drive at that speed, but often, in some areas, it is more sensible to be driving at a slower rate. SpeedLimiter allows you to do so. If you do need more speed, to accelerate out of a situation, you just floor the pedal and it overrides the limiter. So, yes you can override it. Yes it does allow you to drive at whatever speed you want below the set limit. The overspeed warning does provide an alternative by pinging as you speed past the limit you have set, which should alert you, just in time, to look up and see the mobile speed camera flash you as you get a ticket. The ping is helpful, but not as helpful as something that stops you speeding in the first place. Apart from Autopilot, I regard this as THE most important driver aid - particularly with the MS, as it speeds up SO quickly. I want to be looking out, at the road ahead, not looking in to see if I am at, or past, the speed limit.
    Created 30-Dec-2015
I currently have an E Class Mercedes (so same switchgear) and I use the Speed Limiter much more frequently than I use Cruise Control. Yes, they are similar, but often I don't want to be driving right at the speed limit, so it is MUCH more helpful to have the limiter selected, so that regardless of how I drive, or accelerate, I know I won't be exceeding the Speed Limit unless I deliberately press through the limiter - which you can do. In a car with the acceleration on the Model S, this would be a major aid. On the test drive, I was speeding even before I had the chance to look down at the speedo! In the Merc, pressing the end button on the Cruise Control lever switches between Cruise and limiter, with all the other functions (push to switch off, pull to apply, short up for 1 mph increment, longer up for 5mph increment, etc). There is absolutely NO danger in driving with this selected, quite the reverse.
    Created 30-Dec-2015

  •  Quite agree with everything said except Andy who should try a car with this feature.

  • On my P85d i love the TACC but some time giving me back the responsability to push harder acceleration without enforcing rules is pretty pleasant and by the way you have always the possibility to push down and go over the speed limit in case of necessity.

  • A MUST for me on my supercar.


    Created 3-Aug-2015
I thought I might be able to accept TACC as a good alternative, but from what I've read, it reacts too slowly (taking 3 seconds or so before accelerating when the car in front has moved to the right), often brakes late (instead of anticipating and smoothly coasting to the speed of the preceding traffic), follows swerving motorcycles without noticing the stationary car in front, accelerates either too slowly or too abruptly, etcetera. And if you ever heard of defensive driving (especially important for agressive drivers like me), well, TACC doesn't have a clue.

So I really wish that limiter arrives before I finally buy my Tesla...

(still waiting for more range to handle my rather long commute)
    Created 22-May-2015
First of all, I like speeding, my cruising speed on european highways is about 30 km/h above the limit. So I'm no speed-limit-obeying pussy.

However, I absolutely love the speed limiter on my Mercedes and use it all the time, as a better alternative to the clumsy cruise control.

While cruising, I just keep my foot resting on the accelerator (which is not fatiguing since you're not modulating it) and the car cruises just like it does on cruise control. So far, not much of a difference there. However, whenever there's traffic, I don't have to toggle any levers or turn anything off. I just smoothly lift my foot and let the car decelerate. Then, when the road is clear again, I push the pedal back down (a little or a lot, depending on traffic further ahead) and I'm back to cruising speed without having had to change any settings. I can drive hundreds of km without ever touching the lever. And it keeps me from speeding more than I intended and getting a license revocation.

With classic cruise control, you're constantly turning it off and back on again, or toggling the lever and getting whatever acceleration rate the engineers decided for you for all circumstances (too abrupt in most cars). It's a pain. It really only works when you drive below the speed limit with little or no traffic.

I thought I would be able to live with TACC as an alternative. But from what I've heard, it reacts too slowly (taking 3 seconds or so before accelerating when the car ahead moves out of your lane), accelerates either too abruptly or not quite abruptly enough, doesn't look ahead, follows swerving motorcycles without noticing the stationary cars in front, etcetera. Driving courses here include notions about defensive driving (anticipating other drivers' actions), but TACC doesn't have any of that, it simply drives like a brain dead robot (which it is).

So please, pretty please, just include the same speed limiter function that's on Mercedes cars which have exactly the same speed limit stalk? Why did they take the same stalk but remove this useful function?

By the way, for those saying "the driver should always be in control": Mercedes has a switch under the gas pedal so it overrides the limiter when you push it in all the way. And of course you can just hit the stalk to turn the limiter off, too. That's really no issue, I've never felt "limited" by the limiter.

One last remark about safety: the psychological threshold for lifting your foot is much lower than the threshold for turning off an automatic system. On cruise control (regular or TACC), you tend to keep going at the same speed even when part of you kind of feels you're going too fast for the current conditions (bend with poor visibility, other drivers doing funny things, etc.). When I'm on the limiter, I often find myself slowing down without even thinking about it. No levers to push, no brake to tap, just lift your foot a little, and push it back down when all is safe. Much easier to do.
    Created 22-May-2015
I currently have a Mercedes with a speed limiter. I love it, and giving it up is my main reservation about switching to a Tesla.

In the (almost never) case I need to override it, flooring the accelerator will disable the speed limiter. So it doesn't limit the driver significantly.

I find it much more convenient than cruise control, especially in traffic.

As a side benefit, in Victoria, Australia, speed limits are somewhat higher than the US generally, and are vigorously enforced. The speed limiter is very helpful for not accidentally going over the speed limit and getting fined. It means that in practice I often travel very slightly faster than average as most people stick a couple of km/hr below the speed limit to avoid being fined due to a fluctuation, and I can get a little closer.
    Created 9-Apr-2015
Aah, one of those people that say you need to be able to speed if once in year you need to speed up to get out of the way of large truck or life threatening obstacle. Just to let you know cars kill more people than guns in US, and the number one reason is high speeds. So if you can save a portion of 45000 people from dying in car accidents yearly by merely, limiting the speeds the cars can go, is worth the rare occasions to "need" (read childish excuse) to speed to "save" yourself from a "life threatening " situation.

Mercedes and Jaguar both have it. It is absolutely safe to have such feature. No one has died in Mercedes or Jaguars because they have it. In fact a lot of people might have actually been saved. In UK where there are average speed cameras along M1 and other highways, a picture is taken at a specified time crossing a highway checkpoint and another is taken once you cross another checkpoint. If your average speed was higher than the speed limit (say 70mph) with a tolerance of 5 or 10mph, you'll get a ticket delivered to your home. This obviously forces everyone, and every single person on the highway to obey the speed limit. This also makes sure that you don't get away by slowing down close to a speed camera and then speeding in the highway and then slowing down again close to another speed camera.

This feature makes sure you can pay 100% of your attention to the road rather, than trying to adjust the pedal to a certain speed and keep looking at your speed on the instrument panel when you are supposed to be looking at the road. Again as I said for Mercedes and Jaguar they are both implemented in the cruise system, so with the flick of a switch it gets disabled and you have the power you need at your disposal.
    Created 8-Apr-2015
Nothing on the car delivers this benefit.

 

A speed limiter is simple and safe plus it protects your licence and delivers responsible reputation for the tesla drivers.
    Created 31-Mar-2015
Unless we're talking about a function within the autopilot, this is the wrong direction.  It is unsafe to limit the driver's capability.  If the human is in charge of the car, the human needs to be able to control the car - and push past a speed limit to avoid a collision or unsafe situation, without fumbling for a speed setting.  The white line and warning chime already present in auto-pilot enabled cars is more than enough to alert the driver to being over the speed limit.

 
    Created 31-Mar-2015
AndyM
3,929
Great idea for people who are new to cars, and may not realize how fast they're really going.  Tesla's software updates could easily install the speed limiter if Tesla considers this feature.  Even if Tesla made cars with combustion engines, Elon Musk could figure it out!
    Created 28-Mar-2015
C'est un must  as we would say. that was my first question when i drove the Tesla for the first time.

it allows you to accelerate without looking to the speed limit a real value with this funny and fantastic accelerating car!!!
    Created 5-Feb-2015
The described Mercedes cruise control sounds fabulous but still has its negative points.  I've never heard of CC functioning this way.  Can the driver manually increase speed over the top set point with just pedal input or are they limited to the top set point until they either set it higher or cancel it altogether?  Depending on the answer this is a negative IMO.  Regardless, the extra feature is a personal choice and one I do not think I would be likely to take advantage of.

I finally took delivery of my S85 in early March.  My driving environment is consistent.  The roads and traffic are suburban and very predictable.  While I have no need for a speed limiter I can intuitively understand its usefulness.  Nevertheless Tesla's Traffic Aware Cruise Control (TACC) has my admiration.  This has been my very first experience with TACC.  It is taking a little while to become accustomed to all of its behaviors but I am working through them.

The one behavior I still do not like, but understand fully, is the very conservative behavior of slowing down longer than a normal human would for the vehicle ahead turning right or left, i.e., the Tesla is still on the brake even though the vehicle ahead has completed the turn for about 1.5 - 2 seconds and is obviously moving away at a ~90 degree angle.  I understand this behavior because when I was a young driver I accidently caused a slow speed rear end collision assuming the vehicle in front of me was going to complete their turn in normal fashion.  You never know what the driver of the vehicle in front of you will do.  When you think about it much of driving is based on assumptions.  Most of the time drivers maneuver their vehicles based on assumptions gained over the course of their driving experiences.  Most of the time is not the same as 100% of the time.  Once I determined I have no way of knowing what causes the Tesla to react this way or the ability to change it programmatically I came to accept it.  Now, when I find myself in traffic on uncontrolled access roads I simply switch off the TACC.

The Tesla TACC on controlled access highways is quite capable in my short time of ownership.  I took an extended trip recently and the TACC performed as expected which allowed me to squirm around in my seat in order to change positions during extended periods of sitting without needing to pay any attention to the speed or following distance.  Insofar as speeding up over the TACC set point, this is a manual maneuver IMO and one I used effectively a few times during my trip.  I did not find it difficult to moderate my top speed because I realized I was back in manual control of the vehicle albeit for top speed and guidance only.

 
    Created 2-Dec-2014
New idea that makes a lot of practical sense ...

Adaptive Cruise Control is of course a step up if it can handle the need to automatically slow down ... but for situations where ACC isn't working or isn't available for any reason, this preset max speed idea is a good one
    Created 1-Dec-2014
JanosB
2,611