ACC reduces my range

[JulianClarity]

I always enable acc because it makes me feel safer, I don't use cruise control. I follow the traffic closer than the settings in the system, sometimes I can feel it brakes for me while I am on the gas paddle. I am getting 42x displayed maximum range, I think it can be higher if I disable ACC, but I would like to keep it on.

 

[Fast Eddie B]

Just curious, how closely do you like to follow?

I ask, because on the minimum setting, ACC seems to put me right on the edge of being too close to following traffic. The rule of thumb is one car length for every 10 mph, though lots of folks certainly follow closer than that. Human reaction time being what it is, I think that puts them at risk of an accident if the vehicle in front brakes suddenly.

As an aside, I consider ACC as a feature of cruise control. Can it be activated separate from cruise control?

 

[RogerB]

I always enable acc because it makes me feel safer, I don't use cruise control. I follow the traffic closer than the settings in the system, sometimes I can feel it brakes for me while I am on the gas paddle. I am getting 42x displayed maximum range, I think it can be higher if I disable ACC, but I would like to keep it on.

Why do you think that? Why don't you disable ACC and see what you get? Evidence > feelings.

You should also edit the title to something like "I think ACC reduces my range"

 

[Groves Cooke]

"I always enable acc because it makes me feel safer, I don't use cruise control."

??????????????? ACC is cruise control!

" I follow the traffic closer than the settings in the system"

?????????? I cannot fathom what you are doing.

 

[Fast Eddie B]

??????????????? ACC is cruise control!

Yeah, it’s actually in the acronym: Adaptive Cruise Control!

 

[fotomoto]

Why do you think that? Why don't you disable ACC and see what you get? Evidence > feelings.

You should also edit the title to something like "I think ACC reduces my range"

If one has the speed set too high for actual traffic flow, that can cause unnecessarily strong acceleration and/or heavy braking. I find that setting the speed to about 5-10 mph + of actual traffic speed and using the spacing feature greatly helps with smoothness.

I think the bigger effect on range isn't ACC itself but the actual driving conditions (speeds, rubber band effect, etc).

 

[2002]

the minimum setting, ACC seems to put me right on the edge of being too close to following traffic. The rule of thumb is one car length for every 10 mph, though lots of folks certainly follow closer than that. Human reaction time being what it is, I think that puts them at risk of an accident if the vehicle in front brakes suddenly.

I have always followed the three second rule which seems plenty close. I was surprised that for ACC three seconds is the the farthest distance, and the closest is one second!

Extra Long = 2.8 second
Long = 2.1 second
Middle = 1.5 second
Short = 1.1 second

Then again it is a computerized system which in theory has much quicker reaction time than a human so maybe the closer settings are safe. It reminds me of the first time I ever heard of adaptive cruise control which was about fifteen years ago on some type of technology show when it was still a rare feature and they were talking about future smart highways and how they will be able to reduce traffic congestion by packing cars closer together at highway speed, something made possible by the then emerging ACC technology. They showed a demonstration on a closed test track with about seven cars cruising along about ten feet apart, it almost looked like a train they were so close to each other. Not saying that would be safe in normal traffic but it does make the point that ACC can in general safely follow closer than a human. But then again we can't always rely on ACC so then you are in a situation where the "backup system" (the driver) might have to react quicker than they may be capable of.
Of course you also have CMBS to help out, but you can't 100% rely on that either.

Then again most people are already following much closer than three seconds so I suppose it's good that they accommodate those drivers, who otherwise might not use the system and miss out on the inherent safety benefits of it.

As an aside, I consider ACC as a feature of cruise control. Can it be activated separate from cruise control?

You can't but it seems like you should be able to. Because of the safety aspects of ACC I find that I am using it pretty much all the time in all kinds of driving conditions, even though the manual (and convention wisdom about cruise control) says you shouldn't use cruise control in heavy traffic conditions. But without ACC active you only have CMBS but that will react only in extreme situations, and it reacts more at the last moment and more abruptly. I think it's safer to use ACC whenever possible since it quickly reacts to any situation where a driver slows down in front of you. Although it may not be urgent at that moment, any time the car in front of you slows down and reduces your distance behind them it is setting up the conditions for an accident, so immediately backing off is the safest thing to do, which I do on my own anyway but I like ACC because it often reacts quicker than I do. It also gives the car behind you a chance to slow down, or at least notice that things are slowing down ahead, whereas if you wait until the situation suddenly gets ugly and you only have CMBS (or your own foot slamming on the brakes) then you increase the chance of being rear ended by a not fully engaged driver who is following you.

 

[Chuck]

You could say we have two cruise controls. With the MAIN button on but ACC off press and hold the (interval) button for one second.

This switches to go old fashion cruise control, you set the speed and manage the traffic yourself

To switch back to ACC press and hold the button again for one second.

Problem in my city(and most others I have visited) if you leave a safe distance someone will dive into it and the Clarity kinda panics and slows very abruptly. My sisters XC60 does seem a bit smarter and seems to measure the deceleration of the incoming car(maybe senses it sooner), it lets the distance shrink a bit and then eases it back out. It just seems smoother, of course it is a $60k car, the lane holding is not much better.

 

[2002]

Problem in my city(and most others I have visited) if you leave a safe distance someone will dive into it and the Clarity kinda panics and slows very abruptly.

That's similar to the other ACC that I have used which was on a rented Infiniti QX80. Human reaction seems much quicker in those cases, we see that the car is moving into our lane before the ACC system does, perhaps because the other car is not yet fully in the radar range. Maybe the XC60 has a wider view. So what I do is the moment I see someone coming into my lane I don't wait for ACC to see it I immediately cancel ACC which starts a slowdown, or press the regen paddle, or touch the brakes, whichever is appropriate depending on the situation.

This is a dilemma that exists in probably most cities, if you leave a safe distance then people cut in. So most people follow closer to avoid that, thus people drive less safe because of anticipation of discourteous driving by others. And then when someone does cut in front of them they often don't back off, just to show the other person their displeasure. I admit that I have done that, but when I do I immediately get on myself for doing something unsafe just to prove a point to an unknown person that I will never meet. That is unless they brake suddenly and I rear end them in which case we will become well acquainted. I would rather avoid that so I put emotion aside and just back off when someone cuts in front of me.

The other problem is when you need to move over because your turn or exit is coming up, if you signal then invariably instead of making room the other driver will speed up to close the gap. For that reason many if not most people don't signal and just pop in. So again doing something unsafe because of anticipation of discourteous driving behavior by others.

Whenever I think about topics like this I think autonomous driving cars just can't get here fast enough.

 

[Danks]

I have always followed the three second rule which seems plenty close. I was surprised that for ACC three seconds is the the farthest distance, and the closest is one second!

Extra Long = 2.8 second
Long = 2.1 second
Middle = 1.5 second
Short = 1.1 second

I learned it as a 2 second rule for daylight, dry pavement, light traffic. Add a second for visibility issues - rain, snow, fog, darkness, higher traffic. Add another second for slippery roads.

I am somewhat dismayed that 2 of the 4 ACC settings are tailgating. At least I will understand what is happening when someone comes up behind me and starts tailgating me, speeding up when I speed up and slowing down when I slow down.

With respect to the OP. ACC may very well reduce the range. Following closer than the ACC settings isn't following - its drafting.

 

[DucRider]

If you try and maintain a 3 (or even 2) second gap in most metro areas while in moderately heavy traffic, you'll soon find yourself nearly stopped. A gap that big invites people to merge into the "hole", requiring you to slow down, opening another hole. Repeat, repeat, repeat...

I find the main problem with the ACC is that it doesn't see anything other than the back of the car directly in from of you and has no ability to anticipate the "flow". This is part of the reason for the jerky/hard acceleration and braking.

That being said, I found ACC at least somewhat useful while in a parade. The Clarity Electric has "creep mode" permanently on (even in sport with full regen selected by the paddles - no "one pedal" driving option). Using ACC meant i did not have to ride the brake to keep it to walking speed for several miles (along with the stops and starts inherent in a parade). The only way to stop "creep mode" is to engage brake hold - but that only works if you are stopped and does nothing when driving in slow traffic (a parade is an extreme example). We'll see how long Audi sticks with that model on the e tron (they also have virtually no regen available other than the brake pedal). "Creep mode" and default regen levels are something that would be easy to set as an option that the user can select - and should be. Probably my biggest gripe about the Clarity.

From some of the accounts related PHEV owners, I think the cruise/ACC on the Electric is a bit better. Can set it as low as 25 mph, and it will coast above the set speed downhill. Easy to feather the throttle to smooth out some of the abrupt slowing/acceleration. An example would be when coming up on a slower vehicle in your lane and needing to wait for the left lane to clear before switching. Engaging the throttle will let you actually slow the car gently and moderate speed until you can switch lanes. After doing so, I find it best to gently accelerate to with a couple of mph of the set speed before lifting off the throttle and letting the ACC take back over. No brake pedal required, no sudden slowing or wasteful acceleration as ACC has a tendency to want to do.

 

[JulianClarity]

You could say we have two cruise controls. With the MAIN button on but ACC off press and hold the (interval) button for one second.

This switches to go old fashion cruise control, you set the speed and manage the traffic yourself

To switch back to ACC press and hold the button again for one second.

Problem in my city(and most others I have visited) if you leave a safe distance someone will dive into it and the Clarity kinda panics and slows very abruptly. My sisters XC60 does seem a bit smarter and seems to measure the deceleration of the incoming car(maybe senses it sooner), it lets the distance shrink a bit and then eases it back out. It just seems smoother, of course it is a $60k car, the lane holding is not much better.

That's the headache I am having, in the bay area. I always want to keep a distance like suggested in the driver's handbook, but it ia impossible.

 

[JulianClarity]

Just curious, how closely do you like to follow?

I ask, because on the minimum setting, ACC seems to put me right on the edge of being too close to following traffic. The rule of thumb is one car length for every 10 mph, though lots of folks certainly follow closer than that. Human reaction time being what it is, I think that puts them at risk of an accident if the vehicle in front brakes suddenly.

As an aside, I consider ACC as a feature of cruise control. Can it be activated separate from cruise control?

From what I think to be, acc means it assists you to keep a safe distance with the forward traffic, cruise control does the work to keep you close to a preset constant speed. It is literally impossible to do cruise control during week days in my area. I am a cautious driver, although I know what I do is dangerous in your eyes, trust me, it is at least safer than 60% drivers here.

 

[2002]

If you try and maintain a 3 (or even 2) second gap in most metro areas while in moderately heavy traffic, you'll soon find yourself nearly stopped.

I always want to keep a distance like suggested in the driver's handbook, but it ia impossible.

That sounds a bit like the old excuse "I can't go the speed limit, if I try I will get run over". Neither are true, you can go the speed limit (just don't do it in the faster lanes) and you can keep a safe distance between the car in front of you. You may not get to your destination quite as quickly but you increase your odds of getting there.

Just as a test, try keeping a safe distance for one commute. Oh I'm sure someone will pop into the gap, and it will probably happen more than once. But count how many times it happens and estimate how much time it costs you. Or do a calculation:

Let's say average speed in traffic is 55 mph. That's 80 feet per second. You're trying to keep a two second distance, that's 160 feet. Car cuts in front of you, average car length is about 15 feet. Presumably someone like that won't be leaving a two second gap between the car in front of them, so let's say they leave half of that which is 80 feet. So each car that cuts in front of you sets you back about 100 feet. And I'll just assume that each car that cuts in front of you never leaves your lane for the rest of your commute (even though in reality many will). So okay say during your commute it happens ten times, so that's 1,000 feet. At 55 mph that's about twelve seconds. Oh so it actually happens twenty times during your commute? Okay so then that's twenty-four seconds added to your trip. If in fact it really does happen twenty times during a commute.

 

[The Gadgeteer]

I do think a human driver can drive more efficiently than ACC. ACC is probably mixing in more friction brakes than a human who is good at using regen. However, ACC is more about convenience than efficiency.

 

[2002]

I do think a human driver can drive more efficiently than ACC. ACC is probably mixing in more friction brakes than a human who is good at using regen. However, ACC is more about convenience than efficiency.

I agree that the somewhat increased slowing down and speeding up caused by ACC does probably use up a little more fuel/charge. However I doubt if friction brakes are used. Then again I am having trouble finding information on when friction brakes are used with Clarity. I come from the Prius world where friction brakes were only used for hard stops, and for the last 5 mph of normal stops. A world where brake pads and shoes can last for the life of the car. My 2006 Prius had 156,000 miles on it when I traded it and the last time I checked the front pads were only half used, the rear shoes were still within limits but I was planning to replace the shoes just to be proactive.

Of course we have no idea yet what brake pad usage will be like on the heavier Clarity, but still I am assuming that for most stops regen is used almost exclusively with very little use of friction brakes. Oddly the manual makes no mention of the brake pedal using regen, at least that I could find. It only mentions regen in relation to coasting and using the paddles to increase regen. And yet on the information display you can see that regen occurs when you step on the brake pedal.