Adaptive Cruise not so great at noticing merging cars

Yes, and it keeps thinking the car is still ahead for a while when it pulls off to another lane or exits. You still have to drive.

 

It isn't full autonomy - the DRCC will often catch a merging vehicle, but (and I think the Manual suggests it) we need to be prepared to take action instead - it seems to be locked on the vehicle it's tracking. If it isn't tracking a vehicle already, it will work better.

With exits, I suspect that it "thinks" that the car you were following and has veered off will be where you're planning on heading too, like on a windy road.

 

From my experience, it seems to want merging cars to cross into 45-55% of the lane before adjusting it's lock. When a locked car leaves the lane, like when it takes an exit but you continue straight, it seems to hold the lock until the car has vacated 95-105%. That last bit gets annoying if the exiting vehicle slows and the Prius brakes despite having, effectively, an open lane ahead.

 

Current automotive radars have a beam width of 3-5°. The resolution is nowhere as good as the optical sensors that are probably better than 0.1° and it can't see the lanes. That makes it difficult for the radar to accurately detect when a car enters or leaves the lane ahead.

kevin

 

I was out driving today, and I noticed twice that I sub-consciously cancelled C/C off, then immediately hit resume as it was slowing for a car exiting. Not sure if I do that when someone merges?

It's a bit like (in a Manual) putting the clutch in, changing gears, clutch out - hundreds of times in a trip - it's an automatic function, you don't think about it, similarly, you turn indicators on without tinking.

 

I guess my expectations are somewhat low for DRCC, I just want it to do the basic job of following the car in front of me on long drives.

I have used cruise control since 1980 when I installed a DIY aftermarket version on my 1977 Datsun. You literally glued a magnet to your driveshaft and mounted the sensor next to it. It actually worked quite well. I just couldn't believe how much cruise control reduced fatigue on long drives. I made sure that every car that I bought after that had built-in cruise control, even if that meant going with a higher option package than I normally would have. Although it has now become pretty much standard so everyone expects it.

I always understood that if a car merges in front of me I have to either adjust the cruise or cancel it and take over. That I could accept. What I always hated though is on long drives and coming up on someone slower and having to adjust the cruise speed, even worse when they were not using cruise themselves so their speed is constantly changing and I have to either keep adjusting or just switch to manual.

So when I heard about radar cruise control it sounded like a dream come true. I have used it once on a rental car and it was a dream come true. I realized very quickly that it doesn't handle situations where someone cuts in front of you with little distance, but I'm okay with that as I never expected early systems to be that robust. We are still in the infancy of self-driving cars.

My only concern is reports that the Prius DRCC shuts off if it no longer sees a car in front of it. That is NOT my expectation and I hope that is just an anomaly that occurs occasionally and will eventually be corrected.

 

It happens. It happens when it was actively following a vehicle and then something "anomalous" occurs where it loses the active lock. It expects there's a vehicle there, but it suddenly doesn't have confidence in the radar data. In that case, it disengages, beeps, and displays a message.

I've had it happen in the rain. More frequently, when going around a bend where there are obstacles like construction barrels, debris, or walls near the edge of my lane. Cases where the radar becomes confused.

In that situation, disengaging is about all it can do. Continuing to accelerate could be dangerous, and the same for suddenly braking "just in case" since it doesn't know about traffic to the rear.

When the system is actively following a vehicle and it moves aside or out of range normally, the system handles it just fine without disengaging.

 

That's good to hear that it only happens in those situations.

 

The only time that happens is if you're under the threshold of "Ordinary" Cruise Control, which it reverts to (under 45km/hr here).

 

There is one situation where it is intentional by design. If you are following a car at 25mph or slower and lose signal it will disconnect.

I was surprised it did that but I believe the design intent is to avoid suddenly accelerating to a high speed if you are following a car round a corner and it loses signal.

kevin

 

Yes, it just reverts to being a non-DRCC without a car in front, which would also cut out below that speed.

 

I've found that if it loses the vehicle in front, mine continue to operate as normal after telling me there no preceding vehicle, but DRCC then picks up again by itself when something comes into range.

 

That's only if your speed is greater han 25mph. If less it will disengage.

 

One other thing to note that I don't think most people understand about DRCC. DRCC will only work if you are approaching a car that is MOVING in the SAME direction as you. If you approach a car that is completely stopped, DRCC will ignore it and slam into the back off it.(actually PCS will kick in and slam the brakes a few ms before you collide, but you'll still hit), likewise if you approach a car that is moving in a different direction than you(towards you, parallel at an intersection)

Also the radar unit has built in self-calibration. It is supposed to be recalibrated every time it or the bumper is removed/replaced. It also self-calibrates over time, so you will notice it might improve over time if it wasn't initially properly calibrated(extremely common). It can self-aim left/right and up/down.

 

Not all the time - might depend on your speed. I have a regular commute where there is a gentle downhill RH curve (we drive on the LEFT!!), 55-60km/hr and occasionally there is a car or 2 parked on the side of the road - the first time I drove there, it "saw" the car, and I'm not sure whether it was DRCC or PCS, but it braked hard and would have easily stopped in time had I continued on that path (was a year ago). Except that my steering around the curve was taking me around the parked cars, and out of their path, so it resumed. Since then, if there is a car parked there, I give it a wider berth and it's not repeated the situation.

 

Same for me Alan, but my curve is in the trough of a small valley. When close to the bottom and the road has an elbow curve into a climb and my DRCC applies the brakes every time regardless of traffic. I've found that either using the accelerator, or dropping the DRCC briefly works for me.

 

The DRCC dropout happens to me from time to time. But it dosen't happen when there is no car in front of me.

So whats the issue that causes the DRCC to shut itself off. Most of the time I can restart it,

 

This has been discussed extensively in another thread just a few days ago.

The bottom line, for me and some others is:

Cruise control is NOT designed or intended to be used in "heavy traffic" or other difficult situations.
It just is NOT.
If you insist on using it anyway, you have no place to complain about how it doesn't do exactly what YOU think it should do.

Using any variety of cruise control in heavy traffic, heavy rain, snow......is NOT SAFE.

 

DRCC is safer than cruise control though, it will adjust speed to the person in front of you.

I have used it in times of relatively poor visibility and found it made me and my driving safer overall. Obviously I pay attention to it and intimately know how it works and what it's limitations are on a technical level.

I mentioned my earlier comment because If you come up to a red light with cars already stopped, but you're not already tracking someone, the car will not recognize the stopped cars and will slam into them at full speed. Every single time, it's just how it works. The system is not designed to detect a car unless it is moving in the same direction as you.


One other thing, you know DRCC vs PCS, if DRCC slows your car down it is gradual and your dash will show the car and the set distance.

If PCS is stopping your car it just flashes red "BRAKE" really loud/bright and SLAMS the breaks.

One other thing, the drive mode effects DRCC, unlike gen 3. If you have it in ECO it won't accelerate as fast, and it won't hold the speed so aggressively up hill. PWR mode will make it try as hard as possible to maintain speed(more accelerator and brake application, worse fuel)

This means if you put it in eco and the car in front of you moves out of the way suddenly you won't accelerate nearly as fast. This is perfect for if the car in front of you keeps going in and out, or around curves.