Radar cruise control/brake assist - danger awareness - Mazda CX3 Forum
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post #1 of 8 Old 12-24-2015, 05:36 PM Thread Starter
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Radar cruise control/brake assist - danger awareness

Thought I'd share a dangerous situation with radar cruise control/brake assist active.

I was traveling in the far left lane on the freeway with radar cruise control. For clarity, the two left lanes are express/hov lanes unaffected by traffic in the right, general lanes. Traffic two lanes to the right (general purpose lane) slowed down significantly, and the freeway curved slightly to the left. At that point I made a lane change to the right.

All of a sudden the car brakes very hard. I suppose either the cruise control or brake assist picked up the show traffic to the far right and decided to brake. Luckily, the car behind me reacted and didn't hit me, but it was a close call.

Lesson? Be wary of brake assist and radar cruise control when speeds between lanes change suddenly and have a large differential.
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post #2 of 8 Old 12-24-2015, 05:40 PM
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What speed were you doing when the brakes applied?

Currently CX5 SportNav 2.2 diesel automatic and AWD.
Formerly CX3 SportNav 1.5 diesel automatic and AWD.

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post #3 of 8 Old 12-24-2015, 06:13 PM
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Quote:
Originally Posted by inflex View Post
Thought I'd share a dangerous situation with radar cruise control/brake assist active.

I was traveling in the far left lane on the freeway with radar cruise control. For clarity, the two left lanes are express/hov lanes unaffected by traffic in the right, general lanes. Traffic two lanes to the right (general purpose lane) slowed down significantly, and the freeway curved slightly to the left. At that point I made a lane change to the right.

All of a sudden the car brakes very hard. I suppose either the cruise control or brake assist picked up the show traffic to the far right and decided to brake. Luckily, the car behind me reacted and didn't hit me, but it was a close call.

Lesson? Be wary of brake assist and radar cruise control when speeds between lanes change suddenly and have a large differential.
I actually think it's written in amongst all the warnings etc. for the radar cruise control in the instruction manual.

I too have had a few odd moments (sort of like You describe), so I generally cancel the cruise control in tight bends with a lot of traffic.
But overall I really love the radar cruise control, I only wish it would work down to standstill and not cancel it self at 30 km/h.

I had a Volvo XC70 rental car a few weeks ago in the UK. It was nice to just let it brake and accelerate when driving in a queue on the M25/M40.

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post #4 of 8 Old 12-25-2015, 07:47 AM Thread Starter
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Was going about 66mph. Car braked hard to about 40mph before I stepped on the gas and overrode the auto pilot.
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post #5 of 8 Old 12-25-2015, 09:35 AM
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OK I was wondering which system was working and that's the smart cruise control. A mate of mine had a little experience with the SCBC on a VW. There was a line of stationary cars but he wanted to turn left (don't forget we drive on the left) and as he knew there was room behind the last stationary car, he attempted to make a normal turn behind it but as he got close to the last car, it dumped the brakes and stopped him dead.

I suppose these systems improve safety for the most part but they don't have human instincts and we have to be wary of the quirks. In reality, both systems were working as designed.

Currently CX5 SportNav 2.2 diesel automatic and AWD.
Formerly CX3 SportNav 1.5 diesel automatic and AWD.

All advice is given in good spirit and taken entirely at the readers own risk. WORK SAFELY. ©2018 anchorman

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post #6 of 8 Old 12-25-2015, 05:34 PM
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Another thing to remember is these systems are not adaptive as they can't scan from left to right when in a turn. They face straight ahead. If you are in a gradual or sharp turn they will see traffic in the adjacent lanes and react.
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post #7 of 8 Old 12-25-2015, 08:05 PM
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Interesting! I have been griping that we in Canada don't even get the adaptive cruise or brake assist. But maybe we should count ourselves lucky instead.

Good that you posted that warning. If it is buried in the instructions somewhere it will not be noticed by most and it is likely to happen to somebody sometime with tragic results.

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post #8 of 8 Old 12-26-2015, 09:47 AM
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Give it another 5 to 10 years and they will have this technology down pat. Unfortunately for now current drivers will have to be aware of the unpredictability of these systems in certain conditions. I think in the fine print somewhere Mazda does warn about over reliance on these systems. Although when it happens unexpectadely this safe technology could turn deadly.

In Australia a few years back a Volkswagen Golf suddenly decelerated on a highway killing the owner when a truck smashed into the back of the car by the unexpected car behavior. Hopefully the CX3 won't have any major problems like this.

Death prompts VW owners to speak out
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