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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Speed limiters
Date: Sun, 7 Jul 2024 09:00:06 -0700
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On 7/7/2024 3:11 AM, Robert Roland wrote:
>> Does the second mode NOT maintain speed but, rather, just act as a warning
>> mechanism?
> 
> Yes, that's correct. It allows me to let off the gas, or even brake,
> when approaching a tight corner.

So, it really only shares the user interface with the cruise control;
the function is different.

>> So, you have to call for *hard* acceleration to overcome its setting.
> 
> Yes, as an alternative to pressing the button to turn it off, of
> course. I assume it is intended as a safety or emergency feature.
> Imagine you are starting to overtake and forgot that you have the
> limiter engaged. Maybe you will slightly panic and not think to press
> the button or maybe not be able to find the button quickly enough. You
> can just "floor it" and off it goes instantly.

I essentially have to take my foot off the accelerator for it to maintain
a particular setting (or, keep it very "light").  If I apply *any* pressure,
it biases the current setting for as long as that pressure exists.  I
don't have to be "forceful" in my assertion.

>> I can increase the vehicle's speed beyond the setpoint with any
>> pressure on the accelerator; letting up on it will bring the car back to
>> the setpoint (using engine braking).
> 
> Yes, in normal cruise control mode, that's how mine also works. Mine
> will even engage the friction brakes if the speed is much over the set
> speed.

Nothing for the cruise control touches the brakes.  It relies on the engine to
slow the vehicle.

There are newer "collision avoidance" systems that will actively brake
if they sense you're approaching an object with which you may collide.

Newer cruise controls will adaptively adjust speed to prevent you from
creeping up the backside of the vehicle in front of you.

>> The article referenced "new regulations" that will require the feature to
>> be reenabled, by default, with each start of the vehicle.
> 
> I don't doubt that it will happen in the future. Laws are governed
> mostly by politics and bureaucracy, and only very little by science.
> 
>> Most US cars won't allow the cruise control to be set below, e.g., 40MPH.
>> I think the reasoning is that you should be actively controling the
>> vehicle in those settings where regulators have decided the speed limit
>> should be low.
> 
> Sounds like a terrible idea to me. Keeping a very low speed is
> actually quite difficult, and requires some attention. I'd rather
> spend that attention on the traffic situation around me.

The assumption is that you are capable of operating the vehicle.
The "need" for cruise control arises because of those periods
where you are trying to maintain a speed for very long periods
of time (e.g., highway driving).  In situations with low speed limits
(e.g., residential areas), you likely WON'T be maintaining a constant
speed for more than a block as there will be a cross street that
you will have to "approach safely" for other traffic.  Or, people
(children) and vehicles entering/exiting the roadway at even more
frequent intervals as they access their individual driveways.

You certainly wouldn't need (want!) to use it in a parking lot
for similar reasons.

I routinely use it on my trips to the local branch library as
the road entices you to exceed the speed limit (a favorite spot
for "enforcement" activities).  I can set it to 50MPH (the
limit is 45) and be reasonably safe from catching the
attention of a police officer.

[Most roads "in town" have a 45MPH limit -- with traffic
entering and exiting the many businesses that line the roadways]