Issue with Emergency Braking System - Nissan Leaf 2020

[Victor Emanuel]

Hello everyone,

I own a 2020 Nissan Leaf, which is still relatively new with only 20,000 miles on it. Recently, I was involved in an accident where the vehicle's automatic emergency braking system did not function as expected. I would like to understand why this system did not activate and what steps I should take to address this issue.

Incident Details:

• Date and Time of Accident: 18 July 2024, 11:55
• Road Conditions: Dry road, no obstacles
• Situation: I was making a right turn at a speed of 8 mph/h (according to the dash cam). A vehicle in front of me stopped at a pedestrian crossing. I did not see it in time and was unable to brake in time. Since I was not fully aligned, I hit the rear-right of the vehicle with the front of my car (the front camera is now non-functional).
• No warning, no auto-brake, nothing.

My Assumption:

• The car was not extremely dirty, but it was not completely clean either. I suspect that since I was turning right (the right turn signal was on), the camera/radar might not have detected the vehicle in front in time and might have been slightly obstructed by dust. However, I do not believe dust was a decisive factor.

I would appreciate your opinions on this incident and any recommendations for next steps. It is important for me to understand why the Automatic emergency braking system did not activate and what measures I should take to prevent such situations in the future.

Thank you in advance for your help.

Here is the recording from my dash cam:

 

[BillAinCT]

I believe the AEB is done by radar not by camera. Did you check for DTCs with a ODB device? If you're coming up fast to a light and the car in front of you is stopped do you get the big dash warning that you're approaching too fast and impact could be imminent?

I've had the AEB save me twice now, both times from a car coming from the right across my bow preventing a T-bone. The first time I was actually accelerating to get across a parking lot entry and still had my foot on the accelerator and it stopped me fast with what sounded like violent ABS activity.

Backing up may be done by camera as I was stopped hard from backing into a wall. I actually got out to see if I had hit it because the stop was so sudden.

 

[knightmb]

I was making a right turn at a speed of 8 mph/h (according to the dash cam). A vehicle in front of me stopped at a pedestrian crossing.

Did you have your blinker on? There is a combination of low "forward" speed and blinker turning that puts the system to sleep to prevent constant annoyance "braking" when following close behind another car when turning. I'll have to research it more myself, but I do know the system is using the radar for the front and sonar for the back. Also, the sensor array can only shift its aim following the turn by less than 60 degrees. I'll have to read up on the tech documents, so don't quote me on any of this, it might be wrong.

 

[Bombastinator2]

when I hear the phrase “emergency braking system” I think about a totally mechanical system that locks the rear wheels and usually has some sort of lever or pull handle. I take it you’re referring to something different.

 

[knightmb]

Ok, now that I found the correct manual here: https://www.nissan-cdn.net/content/...s/leaf/2020/2020-nissan-leaf-owner-manual.pdf
Because trying to read through 600 pages in my own manual without a search function is brutal...

Basically, you have radar in the front, side radar in the back for cross traffic, sonar in the middle for backup collision detection and the camera in the front is also part of the front collision system, but only for pedestrian collision detection. This all begins on page 349 for those that want to read all the technical stuff, but I'll try to summarize here.

The front "radar" part is using a sensor array that follows the direction that you steer. The limit is 60 degrees, anything beyond that is beyond the view of the radar sensors. Using Front Camera Motion detection Mode, you can see exactly where the radar is "looking" with this view, I've attached some camera shots from my own to help with the visualization of this below.

Straight View

Turning the Wheel View

Full Turn Wheel View

So, without just spitting out a bunch of technical jargon here, my theory is that the wheel was turned to the right, the sensors were looking that way and the car you hit just happen to come in from the sensor blind spot before it could react to it. This does point out the edge cases where the front collision will fail, so at least in this sense, you've helped the rest of us learn the limitations of the system and to be more careful.

 

[knightmb]

Finally, for the Pedestrian Emergency Braking, I have 2 times that it has activated on mine, saving me from hitting someone who carelessly just walked out in front of me, luckily both times I was traveling at speeds under 25 mph and I saw them do it, but the Leaf reacted faster than I could because when I smashed in the brake, it was already down and stopping.

 

[Bombastinator2]

So you’re saying that because his wheel was cranked over all the way the LiDAR wasn’t looking at the car. The leaf already has an exceptionally bad turning radius. I fear that if thy think this needs to be fixed and this is the actual issue rather than widening the radius of the LiDAR future models will have an eve further gimped turning radius. I already have to do a 3 point turn to get into my parking stall and have a tendency to park cockeyed because it’s so bad. This may turn out to be very bad news in the future.

 

[knightmb]

I suspect it is just a limitation of what the system is suppose to do. If you use ICC for example and you follow behind a car on a curvy road, if the curve is great enough, it will lose track of the car and behave like it is no longer in front of you. So, it will cause you speed up and once you get close enough to the lead car, it tracks again and you slow down, sometimes rather quickly as it kinda panics. My guess is; ICC is not suppose to be used this way (open highway versus blind curb) when following another vehicle, but it is a good real world example you can try that points out the limitations of the system. It behaves nearly identical to AEB in terms of tracking possible collisions.

In the above example that the OP has given us, the AEB is probably looking to the right so as not to "turn" into another vehicle by accident. If it only looked forward, then AEB would be triggered every-time another car was driving past the opposite direction but in no way going to actually hit you, which means it would be constantly slamming the brakes on drivers in a very nuisance type of way. The owners manual does mention that if a vehicle rapidly enters into the tracking field too fast, it may not be recognized fast enough to avoid a collision. The video is only 2 seconds long, but it took less time than that for the other vehicle to speed by and then slam on the brakes and cause a fender bender. Good thing the OP was only doing 8 mph.

Even the OP didn't notice this vehicle because he probably assumed that once they went by, he was looking left to make sure no other vehicle was coming down the street before turning and had no idea that the vehicle that just sped past him, just slammed on the brakes right in front of him. I've had this happen to me many times as well and nearly hit a vehicle as I was turning because they blew past me, then slammed on the brakes right as I was turning. I was lucky though, I slammed on my brakes fast enough not to hit them. My AEB never went off either now that I think about it, so I've also experienced this sensor blind spot I just realized...

AEB has a lot of "false" detection events under the right circumstances. One that I know of is when following a vehicle and they turn right for example, but they turn so slow that you have to kind of "veer" around them, usually sets off the first warning level of the AEB but no sudden brakes; until you get past them. Interestingly enough, stationary vehicles on the side of road are ignored quite well, so it seems it does "track" the vehicle ahead of you if it is moving.

Having written all that, I don't depend on AEB. It's nice to have as a backup because it has saved my butt quite a few times over the years, but I know it's not a flawless system and anything that happens is still on me as the driver.

 

[BillAinCT]

For Pedestrian EB I've had it trigger on a curve with a pedestrian walking on a sidewalk that to the car looked to be in its view and approaching. It killed the motor but had not applied the brakes as it saw the pedestrian get out of the view. And then motor power was restored. It was a very odd sensation because I thought "Oh no, my LEAF died!!".

 

[Victor Emanuel]

I believe the AEB is done by radar not by camera. Did you check for DTCs with a ODB device? If you're coming up fast to a light and the car in front of you is stopped do you get the big dash warning that you're approaching too fast and impact could be imminent?

I've had the AEB save me twice now, both times from a car coming from the right across my bow preventing a T-bone. The first time I was actually accelerating to get across a parking lot entry and still had my foot on the accelerator and it stopped me fast with what sounded like violent ABS activity.

Backing up may be done by camera as I was stopped hard from backing into a wall. I actually got out to see if I had hit it because the stop was so sudden.

I didn't check for DTCs (diagnostic trouble codes). Now my car is at the service center, but luckily I had insurance. Yes, the big dash warning did appear many times in the past, but not during this accident.

I suspect it is just a limitation of what the system is suppose to do. If you use ICC for example and you follow behind a car on a curvy road, if the curve is great enough, it will lose track of the car and behave like it is no longer in front of you. So, it will cause you speed up and once you get close enough to the lead car, it tracks again and you slow down, sometimes rather quickly as it kinda panics. My guess is; ICC is not suppose to be used this way (open highway versus blind curb) when following another vehicle, but it is a good real world example you can try that points out the limitations of the system. It behaves nearly identical to AEB in terms of tracking possible collisions.

In the above example that the OP has given us, the AEB is probably looking to the right so as not to "turn" into another vehicle by accident. If it only looked forward, then AEB would be triggered every-time another car was driving past the opposite direction but in no way going to actually hit you, which means it would be constantly slamming the brakes on drivers in a very nuisance type of way. The owners manual does mention that if a vehicle rapidly enters into the tracking field too fast, it may not be recognized fast enough to avoid a collision. The video is only 2 seconds long, but it took less time than that for the other vehicle to speed by and then slam on the brakes and cause a fender bender. Good thing the OP was only doing 8 mph.

Even the OP didn't notice this vehicle because he probably assumed that once they went by, he was looking left to make sure no other vehicle was coming down the street before turning and had no idea that the vehicle that just sped past him, just slammed on the brakes right in front of him. I've had this happen to me many times as well and nearly hit a vehicle as I was turning because they blew past me, then slammed on the brakes right as I was turning. I was lucky though, I slammed on my brakes fast enough not to hit them. My AEB never went off either now that I think about it, so I've also experienced this sensor blind spot I just realized...

AEB has a lot of "false" detection events under the right circumstances. One that I know of is when following a vehicle and they turn right for example, but they turn so slow that you have to kind of "veer" around them, usually sets off the first warning level of the AEB but no sudden brakes; until you get past them. Interestingly enough, stationary vehicles on the side of road are ignored quite well, so it seems it does "track" the vehicle ahead of you if it is moving.

Having written all that, I don't depend on AEB. It's nice to have as a backup because it has saved my butt quite a few times over the years, but I know it's not a flawless system and anything that happens is still on me as the driver.

I completely agree, and thank you for your insights! You really enlightened my mind. I had been wondering: how was it possible that I didn't see that car ahead? Now I have an explanation: I was looking to the left, and by the time I looked to the right, it was too late to react. However, that one second felt like ten seconds. I was in slow motion. I think you know this feeling when you're in danger, and time seems to slow down.

So yes, I think I now have the whole picture of why the AEB was not working (I agree with what you said about how, when I'm on autopilot and I turn left or right, it loses track of the vehicle in front) and why I made that crash. My regret is that I wasn't aware enough to press the brake in that moment, but I was able to say something like, "Oh!" as you can see from the video.

Another thing: I use the e-pedal every time while driving in cities, and this is the second time I haven't reacted quickly enough to press the brake. I can't blame the system for not applying the brake, but I think it's more about me being a second too late.

 

[Bombastinator2]

I’m not a big fan of the e-pedal. It makes coasting near impossible and seems to destroy my range.

 

[Victor Emanuel]

I’m not a big fan of the e-pedal. It makes coasting near impossible and seems to destroy my range.

I agree (well, I am a fan of it ). That's why I only use it in the busiest cities where I have to stop a lot, so I don't have to keep my other leg on the brake all the time.
But it's true what you said, range is B-A-D !

 

[BillAinCT]

Another thing: I use the e-pedal every time while driving in cities, and this is the second time I haven't reacted quickly enough to press the brake. I can't blame the system for not applying the brake, but I think it's more about me being a second too late.

The very frustrating thing about e-Pedal: I'm coming up to a light. A car ahead of me is stopped. My foot is off the pedal. So why give me the warning and make me use the brake! The car is stopping for me already so continue to brake harder so I will stop in time.

 

[Bombastinator2]

The very frustrating thing about e-Pedal: I'm coming up to a light. A car ahead of me is stopped. My foot is off the pedal. So why give me the warning and make me use the brake! The car is stopping for me already so continue to brake harder so I will stop in time.

More reason to not use the epedal or at the very least make sure you really want to.

 

[cornbinder89]

As an old geezer, I just don't "get it" when it comes to one pedal driving? I am still mostly a 3 pedal driver.
I can forgive a human for making a mistake far easier than I can a machine or program.
My wife will not even use cruise control, I do, more to make sure I keep to the speed limit.
What is bad or hard about using one for go and one for stop?

 

[BillAinCT]

I don't let it get to the point to really stop for me. Because I would feel more than stupid to hit the car ahead and say "I expected my car to brake for me". So I do hit the brake of course. Since AEB has saved me twice (once I could have approached and crossed a lane more carefully but the other time a car shot out of a driveway into my lane while I was going about 25). I guess e-Pedal is a preference and some use it and some don't.

I guess lane assist/keep isn't your cup of tea either. Adaptive cruise control with lane assist has allowed me to drive over an hour including slow downs for traffic and merging traffic and never had to hit either pedal. I'm having to do less, which I think is safer. I'm not drifting close to the line or too near the car in front. But alert you must be to avoid others who do drift out of their lane.

For me (also an older retired geezer), the less I have to do or manage while driving the safer I feel. You can't make a mistake doing nothing, right? Can the car make a mistake? That's a whole other topic. Teslas do.

 

[Bombastinator2]

There’s evidence to support that is sometimesfalse..in genisis. God didn’t just throw down the rebels he threw down those who did nothing as well. And that part of the Bible comes from something like 4000bc. So not exactly a new idea. at best situational. A thing like e-brake is really easy to implement. Yet no one else does it. There may be a reason.

 

[Chad E. Mo]

The AEB is not perfect. It has ghost-braked at highway speeds (just a touch, but wth) and it did not activate when someone left-turned* in front of me.

* I was proceeding in an open lane when the other vehicle popped through two adjacent lanes of stopped traffic. Good-Samaritans want to kill you.