Living With Your Adaptive Cruise Control

Part 3

Bad Weather/Visibility

In rain or snow it's often hard to see the car in front of you. And on slick roads, following distance is all the more important. Set the ACC at a speed slower than you expect to travel. If the ACC radar is not covered up, you will see the following distance readout. As I said this is very important on bad conditions.

In this situation you are not depending on the ACC in the slippery weather, which is frowned upon by the Safety people.

Living with Adaptive Cruise Control

Making full use of the safety and speed features built in to the ACC will make your life easier, less stressful, and you shouldn't have to worry about a Safety violation.

Part 3

Bad Weather/Visibility

In rain or snow it's often hard to see the car in front of you. And on slick roads, following distance is all the more important. Set the ACC at a speed slower than you expect to travel. If the ACC radar is not covered up, you will see the following distance readout. As I said this is very important on bad conditions.

In this situation you are not depending on the ACC in the slippery weather, which is frowned upon by the Safety people.

Living with ACC

Making full use of the safety and speed features built in to the ACC will make your life easier, less stressful, and you shouldn't have to worry about a Safety violation.

Wouldn't be safer to not use cruise in poor conditions, ie wet roads, and just throttle slower and keep an eye on your CMS?

UHC asks:

Wouldn't be safer to not use cruise in poor conditions, ie wet roads, and just throttle slower and keep an eye on your CMS?

Absolutely. The ACC might get confused between the wheels spinning at a different speed than the speedometer has.

But if you set the speed at something ridiculously slow, say 22 mph, and then you use the accelerator to get to 50 or whatever is safe, the speed control never kicks in. So you have the distance "meter" when you really need to know that following distance.

I've done this through a few rainstorms and it works for me. Sure, snow or even rain may cover the radar unit, but that's a different story.

Y'all must be driving autoshifts or something. All the trucks at my company (whether manual or autoshift). Have a Bendix.. sensor on the front bumper.. will calculate the distance and speed of the vehicle in front of you and display it on a screen mounted to the dash. If you get too close and the vehicle ahead of you is going slower than you, it beeps continuously.. as you get closer, it beeps faster.. get too close and it'll slam on your brakes. I've only had mine slam on twice. Both times in heavier traffic where some ******bag cut in way to close. Barely a couple feet in front of me, with no warning. It probably saved their life. In one incident a leo witnessed it and pulled over the offending vehicle. Luckily if there's snow etc the sensor gets wonky and disables the system.

But if you set the speed at something ridiculously slow, say 22 mph, and then you use the accelerator to get to 50 or whatever is safe, the speed control never kicks in. So you have the distance "meter" when you really need to know that following distance.

Ok, so your CMS doesn't show the speed and distance of the vehicle in front of you unless cruise is set? Mine shows it regardless if it's on or not.

Unholychaos follows up:

Ok, so your CMS doesn't show the speed and distance of the vehicle in front of you unless cruise is set? Mine shows it regardless if it's on or not.

My experience is with the Freightliner system. The cruise control need to be active to see the distance. So you don't have to fake out your system.

@Susan: my truck is a 2017 F-liner with auto-shift. But today I was privileged to drive a 2015 Pro-star with a Bendix system. I watched the interval time on the dashboard readout.

The system did control the distance at 3.5 seconds and did slow the truck sometimes. But, unlike the F-liner one, the Bendix did not slow down on downhill overspeeding.

The system did control the distance at 3.5 seconds and did slow the truck sometimes. But, unlike the F-liner one, the Bendix did not slow down on downhill overspeeding.

So that Pro Star didn't have IPM (Intergrated (Intelligent?) Powertrain Management) which essential scans the terrain ahead and slows down about 3mph in preparation for a downgrade, and automatically kicks on the jake brake at about 4mph faster than the set cruise, in an attempt to prevent flying too fast down the hill.

I liked having that distance readout. My current truck doesn't have that. I hate to be "that guy," but I have to politely disagree on a couple of things.

I really don't think 3.5 seconds of following distance is enough in most situations. While it's true that the computer can react faster than we can, the computer has only one programmed response if something goes wrong up ahead--hit the brakes. Hitting the brakes is often not the best option, but if you're 3.5 seconds behind someone, it's pretty much all you can do. If you're behind another truck it also limits your visibility, making it harder to see that officer on the shoulder a half mile up the road.

I'm not sure if you were suggesting this or not, but I don't think it's wise to let the ACC control your following distance in traffic. It seemed like you were saying to set the cruise way lower than your actual speed just to see the distance readout, which I agree with. When I was on Target dedicated doing local runs through Denver all the time, we had alot of guys get called into the office for dashcam events because they were using the cruise in heavy traffic. They were trying to cruise with traffic with the ACC on and it kept slamming on the brakes.

The problem is that the ACC can only read the distance of the vehicle directly in front of you, but not two cars ahead or the car next to you about to cut you off. It also can't see that debris in the middle of the road that the truck in front of you just ran over.

Sorry if I misunderstood what you were saying. I'm just not a big fan of using the cruise, even ACC, around other vehicles unless I'm going significantly below the speed of traffic.

Pianoman, you are adding flesh to the bone. I didn't cover every possibility.

First, everyone has their 'druthers. No problem there. The 3.5 second interval is set as a minimum. It's up to you to drive everywhere safely. Using the accelerator, the driver can override this distance if needed (getting ready to pass a slower vehicle).

Of course the driver needs to see what's happening everywhere, front, back, let, right that will affect their driving. That's Situational Awareness.

They were trying to cruise with traffic with the ACC on and it kept slamming on the brakes.

Using a cruise control to manage speed in traffic certainly is a no-no. In my suggestion, the driver sets the control at a really slow speed, say 12 MPH. This is only to turn on the distance readout. Even in heavy traffic you'll be moving faster than the set speed, so the ACC won't really be controlling anything. (Always, pressing the brake pedal cancels the ACC.) I'm sure slow traffic is where truck drivers tailgate too much.

Pianoman, you are adding to the discussion. Thank you!