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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. Deceleration rate is whatever the engineers chose for you and is relatively abrupt on most cars (I haven’t tried in a Tesla). Afterwards, 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 a 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 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 smoothy accelerate withouth 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.

Competitive/Pricing/Notes

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

Unknown.

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Disable Speed Limiter

by RaceDeck

Description

Would be great to have not have a factory speed limiter on the car. We do a number of sanctioned events where we can drive at max speeds ( controlled / legal) and would love to see what the limits are.

Competitive/Pricing/Notes

From Moderator: The speed limiter may be to protect the motor, which is running at about 16,000 RPM at 130 MPH.  This is similar to an ICE car’s tachometer red-zone where the engine is at risk of self-destruction at high-RPMs.

Status

From Moderator: Interestingly the v5.9 software increased the maximum speed indication on the instrument display to 140 MPH, so perhaps a small speed upgrade is in the works.

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Description

A basic option uses a pre-set limit for warning and/or preventing going a specific speed.

To deactivate and change the setting requires a password.  Activation would not require a password. Settings and operation can only be changed while stopped.

This might be used as a parental limit for the kids or as a valet mode where the maximum speed is limited.

A more advanced mode would read the GPS location and identify the speed limit and provide a warning when the speed exceed the map’s known speed limit by a set amount. For locations outside known roads (i.e. parking lots), it might limit speeds to 20 MPH.

Competitive/Pricing/Notes

Unknown if other vehicles have such an option.  Using GPS positioning is not 100% reliable, especially when frontage roads run along a freeway or other close roadways.

Status

The speed warning feature is being added as a standard item in the late September to October 2014 time-period.

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