[StanDiego]

I've read a number of posts lately promoting ACC and have been meaning to ask about BMW's implementation.

I don't have the option in my Z4 but I do have it in my Subaru Outback. At first I really liked it but over time have grown to really dislike it, don't know if it's me or Subaru's implementation of it.

What I like: Set it and forget it. I hit cruise control and the vehicle does the rest, will even come to a complete stop as necessary and then proceed when the vehicle in front of me moves forward, pretty slick. I can even easily change the distance between me and the vehicle in front of me.

What I don't like: It (logically) doesn't have an ability to anticipate slowing down. When ACC is disabled and I see a vehicle several vehicles in front of me apply the brakes (traffic, stop light, etc.), I anticipate it and let my foot off of the accelerator and prepare to slow down and/or stop. With ACC enabled, my Outback obviously doesn't care about anything except the distance to the vehicle in front of me. If that vehicle abruptly slows down, the ACC in my Outback abruptly slows down by applying the brakes.

When going over hills, ACC accelerates to maintain speed but after reaching the apex, it may apply the brakes to slow me down when descending the hill.

So what's my beef? By being unable to anticipate situations, the ACC causes my brakes to be applied much more than when ACC is disabled and I am in control. I don't really know how much more wear it's causing to the brake pads and rotors but I suspect it is significant. On top of that, because it simply maintains a set distance to the vehicle in front of me, it also negatively impacts fuel economy with the more aggressive acceleration/deceleration (compared to manually anticipating and responding to traffic).

Purely speculative but I wouldn't be surprised if the use of ACC cuts the life of my brake pads in half if used regularly. Perhaps it's not a big deal to some/most of you, perhaps the ACC in the Z4 is more refined but I've concluded that ACC in my Outback is going to cost me a set of brake pads much sooner so I rarely use it.

I'm curious to hear and compare experiences with those of you who use ACC in your Z4.

[Horseman]

That's part of the reason why I don't like it. Not to mention, I tend to get better gas mileage with just using my foot rather than using the adaptive cruise control in my Subaru Crosstrek. OR... someone will pop in front of me and it'll slow down and then they'll either change lanes or speed up next thing i know i'm redlining to get back up to speed lol. Honestly.... I drive with my foot on the pedal more than I do with any sort of cruise control, even on long hauls.

[Pprior]

The hills thing is super annoying. We have a Mitsubishi plug in hybrid that is the best ever at that because it has the battery it will apply instant power at the hill and then capture it right back on the way down. Speed stays rock solid.

I live in Florida so no hills now

[RigaTony1982]

I think it works well, especially when traffic is more stop and go or has frequent slowdowns. Now that I have it, I don't think I'd want to go back to regular cruise control.

[Bimmerfun82]

I love it, especially in stop and go traffic. It's nice on a long road trip to reduce fatigue as well. That being said, I very rarely use it.

[gkgeiger]

First, I’ll say I’m glad I have it on both vehicles. There is a love/hate relationship going on. My biggest complaint is when it thinks there is something in your lane that isn’t there and it rapidly slows down. Also, if you get lazy and aren’t paying attention to your speed you could be going much slower than you want because of the car in front of you.

[Horseman]

Originally Posted by gkgeiger

First, I’ll say I’m glad I have it on both vehicles. There is a love/hate relationship going on. My biggest complaint is when it thinks there is something in your lane that isn’t there and it rapidly slows down. Also, if you get lazy and aren’t paying attention to your speed you could be going much slower than you want because of the car in front of you.

Agreed my Long-Trip-Zone-Outs have had me go much slower than I'd like to some times because I'm just simply in my own head.

[Westside Guy]

Originally Posted by RigaTony1982

I think it works well, especially when traffic is more stop and go or has frequent slowdowns. Now that I have it, I don't think I'd want to go back to regular cruise control.

My wife has it in her 228i and that stop and go is the situation where it really comes in handy.

Also one time on the highway I was doing 75 mph with light traffic and it was engaged. I was playing with the radio and took my eye off of the road for a few seconds. Some idiot cut into my lane for absolutely no reason and was less than 2 car lengths ahead of me and it immediately slowed my car down. This jerk continued to slow down so I floored the car and went around him. The ACC definitely served its purpose.

[Horseman]

Just think at the end of the day it comes down to personal preference.

[Westside Guy]

Originally Posted by Horseman

Just think at the end of the day it comes down to personal preference.

We will have to agree to disagree on this option.

At the end of the day, you can lead a 93 octane horse to water but you can't force it to fill up its tank!

[bacampbe]

My wife's M340i had it, and I really liked it. I'm sure it did not see traffic slowing ahead of the lead car, but it never seemed to slow abruptly unless the lead car also slowed abruptly.

I did have a couple of gripes: It needed to be more aggressive accelerating when the lead car speeds up. It would hang back at first and encourage people to cut in. That could turn into an endless cycle of cut-ins unless I forced it to accellerate. And when it slowed due to a slower lead car, it did it subtly enough that I didn't always notice until I was slow enough to make it harder to change lanes. I would like an (optional) chime to tell you when it slows.

Neither of those things would stop me from getting it again, and I ordered it on my in-production m40i.

[GerryC]

I have ACC in the Z4 and DAPP in the X5. Absolutely love having them. In a lot of traffic conditions, they work great: normal traffic where everyone is +/- 10 mph on the freeway, stop and go (especially DAPP with the ETJA). When traffic goes from 60 mph to 5 mph and you can see the slow traffic ahead, I just hit Cancel and let my speed coast down. It can handle it safely, but there's no reason to run up at high speed and slam on the brakes.

It was a great help yesterday as I was on a 2-lane road (60 mph limit) and got caught behind a truck hauling an excavator with a solid stream of oncoming traffic. He was running up and down between mid-high 40s and mid 50s and I was the 4th car behind. The ACC just kept me about 25-30 yards behind with no effort.

[stlcdr]

Not a fan. But, I do not drive in frequent, moderate, traffic. It was also over a grand; not going to pay that for something I'm not going to use.

Indeed, the current, what? 500 bucks? currently is too high (mho) - shouldn't this have been included in the high end package?

I feel like you are giving up an awareness and relying on electronic control: essentially, someone else is controlling [the speed] of your vehicle.

EDIT: This is not a knock on those who use it, just my opinion - if it was a cheaper option I would have added it for resale value as people do like it.

[RigaTony1982]

Originally Posted by stlcdr

Not a fan. But, I do not drive in frequent, moderate, traffic. It was also over a grand; not going to pay that for something I'm not going to use.

Indeed, the current, what? 500 bucks? currently is too high (mho) - shouldn't this have been included in the high end package?

I feel like you are giving up an awareness and relying on electronic control: essentially, someone else is controlling [the speed] of your vehicle.

EDIT: This is not a knock on those who use it, just my opinion - if it was a cheaper option I would have added it for resale value as people do like it.

Should be included as standard, and if not at least as part of the Driver Assistance package. All that stuff in the DAP comes as standard on cars costing 1/2 as much.

[bacampbe]

Originally Posted by stlcdr

Not a fan. But, I do not drive in frequent, moderate, traffic. It was also over a grand; not going to pay that for something I'm not going to use.

Indeed, the current, what? 500 bucks? currently is too high (mho) - shouldn't this have been included in the high end package?

I feel like you are giving up an awareness and relying on electronic control: essentially, someone else is controlling [the speed] of your vehicle.

EDIT: This is not a knock on those who use it, just my opinion - if it was a cheaper option I would have added it for resale value as people do like it.

I had the same argument when we bought our first BMW (2012 328i). But I've changed my mind since then, and I assume the feature has gotten smarter.

The way I think of it now is that I have two "brains" paying attention. At least one doesn't get distracted by scenery, passengers, etc. The odds of both brains failing to react is smaller than the odds of either by itself.

That of course falls down if you just let the car drive and don't pay attention. Fortunately I haven't learned to trust it that much. I do find myself thinking more strategically and less tactically.

[GerryC]

Originally Posted by stlcdr

Not a fan. But, I do not drive in frequent, moderate, traffic. It was also over a grand; not going to pay that for something I'm not going to use.

Indeed, the current, what? 500 bucks? currently is too high (mho) - shouldn't this have been included in the high end package?

I feel like you are giving up an awareness and relying on electronic control: essentially, someone else is controlling [the speed] of your vehicle.

EDIT: This is not a knock on those who use it, just my opinion - if it was a cheaper option I would have added it for resale value as people do like it.

I won't argue the cost. I agree it should be standard, but the options are where most of BMW's profit comes from.

My view on the technology comes from a 40+ year career as an aero engineer and private pilot. Automation in the cockpit has been argued for ages, but the numbers show the benefits. Most of the automation systems I worked involved either workload reduction or protection.

A simple wing-leveler autopilot can reduce pilot workload 50-70%. When flying in the clouds, that's a big deal. A lot of small aircraft don't have an autopilot, but if I was going to be flying one in the clouds regularly, it would definitely have one. Airliners have much more sophisticated 3-axis autopilots and flight management systems. They often fly over 90% of their time on autopilot.

And the same for protection for airline operations. If pilots and air traffic control (ATC) do their job, no aircraft will ever fly into another aircraft or into terrain. They do make mistakes, so there's Traffic Collision Avoidance System (TCAS) and Terrain Awareness and Warning System (TAWS). They have made a huge difference in safety.

These all make the pilot's job easier and safer, but he still has to fly the plane. DAP and ACC are no different. They are driver's aids. They help reduce workload and provide safety backup. You still have to drive the car. But if it's available, I'll take advantage of it.

[stlcdr]

Originally Posted by GerryC

I won't argue the cost. I agree it should be standard, but the options are where most of BMW's profit comes from.

My view on the technology comes from a 40+ year career as an aero engineer and private pilot. Automation in the cockpit has been argued for ages, but the numbers show the benefits. Most of the automation systems I worked involved either workload reduction or protection.

A simple wing-leveler autopilot can reduce pilot workload 50-70%. When flying in the clouds, that's a big deal. A lot of small aircraft don't have an autopilot, but if I was going to be flying one in the clouds regularly, it would definitely have one. Airliners have much more sophisticated 3-axis autopilots and flight management systems. They often fly over 90% of their time on autopilot.

And the same for protection for airline operations. If pilots and air traffic control (ATC) do their job, no aircraft will ever fly into another aircraft or into terrain. They do make mistakes, so there's Traffic Collision Avoidance System (TCAS) and Terrain Awareness and Warning System (TAWS). They have made a huge difference in safety.

These all make the pilot's job easier and safer, but he still has to fly the plane. DAP and ACC are no different. They are driver's aids. They help reduce workload and provide safety backup. You still have to drive the car. But if it's available, I'll take advantage of it.

While I agree that pilot workload is significant, and automation of mundane tasks can help, does that really apply, here? What 'workload' is being reduced so the driver can concentrate on...what?

Are they really aids or are they crutches: ACC is safer not because it aids the driver, but because they are not paying attention in the first place.

Not saying the above is a truism, just a counterpoint argument.

[bacampbe]

Originally Posted by stlcdr

While I agree that pilot workload is significant, and automation of mundane tasks can help, does that really apply, here? What 'workload' is being reduced so the driver can concentrate on...what?

Are they really aids or are they crutches: ACC is safer not because it aids the driver, but because they are not paying attention in the first place.

Not saying the above is a truism, just a counterpoint argument.

On a more practical level--Cruise saves me from leg cramps on long drives. But freeway traffic has gotten so bad in my area that conventional cruise has become nearly useless. I can keep AAC engaged for much more of the time.

[Bimmerfun82]

DAPP is incredible on our X5. I use it for at least half our trip to the beach (320 miles) every time. I pay attention and keep my hands on the wheel, but it drastically reduces fatigue on long road trips and takes better advantage of the eco pro mode than I can with the coasting (which aggravates me when I’m using the gas pedal). Love how it changes lanes for me.

ACC is much less helpful but if I’m going to use cruise control, why not have it? And it depends how you have your safety settings calibrated. I don’t like the steering wheel corrections with that system, so I have those off. If I’m stuck on a 2 lane road with trucks in front of me, ACC is great. If I’m in stop and go traffic on a 2 lane road, also super helpful. Outside of those instances I never use it.

[GerryC]

Originally Posted by stlcdr

While I agree that pilot workload is significant, and automation of mundane tasks can help, does that really apply, here? What 'workload' is being reduced so the driver can concentrate on...what?

Are they really aids or are they crutches: ACC is safer not because it aids the driver, but because they are not paying attention in the first place.

Not saying the above is a truism, just a counterpoint argument.

Automation doesn't give you the ability to 'not pay attention'. Driving, like flying, consists of lots of small tasks that require the drivers attention. Despite people who claim to multitask, it's a myth. You sequentially shift your focus from one task to another. Judging the distance to the car in front and adjusting your speed takes cognitive effort. It also has to share time with lane keeping, watching for drivers that are changing lanes, what's going on behind you, etc. If you can reduce the cognitive effort and time spent maintaining that distance you have more time to deal with assessing your surroundings and identifying other threats.

The primary benefit to me is that it reduces stress and fatigue. That alone is worth it to me.

As far as comparing it to flying, there are certainly times where the workload flying is much higher, e.g. flying an instrument approach in turbulence. But a lot of the time it's actually less effort than driving. One old quote: Flying is hours and hours of boredom interspersed with moments of sheer terror.