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Radar Cruise Control Not To Be Trusted?


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I had an unnerving incident yesterday which has increased my distrust of electronic driving aids even more. I was using normal radar cruise control set at 40 mph in a speed limit area and a car pulled out from a car park into my path but travelling in the same direction as me. It wasn't dangerously close and the radar detection was set to the longest gap so I didn't take any action and expected speed to drop as necessary. But somehow the cruise control didn't react and as the gap closed on the car, which was slowing rather than accelerating, I realized it was too close for comfort and had to slam on the brakes quite hard. Not an emergency stop but a lot more fiercely than normal and upsetting the gear I was carrying in the back. This is not the first time that the radar has not recognised slow moving vehicles when they join the lane or are only partially blocking it. The danger with all such systems is that they lead to a false sense of safety up until the moment when they don't quite work as expected. In future I won't wait before disengaging the system when in doubt. 

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It might be worth spending a little time reading the owners manual - long-winded and complex though it is. The really simple headline guidance states:

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Use the dynamic radar cruise control with full-speed range on freeways and highways.

and in more specific detail later on:

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When the sensor may not be correctly detecting the vehicle ahead In the case of the following and depending on the conditions, operate the brake pedal when deceleration of the system is insufficient or operate the accelerator pedal when acceleration is required.
As the sensor may not be able to correctly detect these types of vehicles, the approach warning may not be activated.

  • Vehicles that cut in suddenly
  • Vehicles traveling at low speeds
  • Vehicles that are not moving in the same lane ...

There's a lot more than I have quoted ... 😉

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Don't suppose they can mimic the intuitive subtleties that the human brain is capable of.

I've only used it in higher speed (national limit) areas where the distance between vehicles is greater - I would feel uncomfortable using it in a 40 limit (purely personal of course). Not something I routinely use as my regular seven mile dual carriageway commute terminates in traffic lights at a roundabout and I can negotiate this with better precision manually given my knowledge of traffic light timing and interpreting traffic density and flow - none of which radar could accomplish.

Interesting to hear other views.

 

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The dynamic radar cruise control takes a little getting used to. We've got the hang of dumb, set-speed cruise control and understand that the car will carry on at the set speed until it crashes (or we take some more sensible action). 😉

The dynamic cruise control probably ought to be thought of as a "follow the vehicle in front up to a set limiting speed". The manual describes it as such:

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In vehicle-to-vehicle distance control mode, the vehicle automatically accelerates, decelerates and stops to match the speed changes of the preceding vehicle even if the accelerator pedal is not depressed.

I am starting to find it very useful on longer motorway journeys - it allows me to happily cruise along but starts to slow when it detects a slower vehicle ahead. I quite like the way that it accelerates again when I turn the right indicator on. I, obviously, still have to drive the car but the only real 'risk' I have found so far is that it almost encourages one to join the queue of middle lane "Volvos" pootling along at 60 ... 🙂

It is obviously going to be very useful while circumnavigating the London Orbital Car Park and similar roads where variable speed limits apply and "going faster than the queue" becomes increasingly silly.

It doesn't work so well on A and B roads. While it may be tempting to let the driver in front do all the work to control your speed it is "quite amusing" when that car disappears around a bend or over the brow of a hill and the RAV then decides to accelerate like mad!  - do it once or twice and then work out that you are better of controlling the car 'manually' ... 😄

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Apart from some brief spells in Lexus LS & RX equipped with ACC some 11-13 years ago, I've got very used to it since doing 39,000 miles in my 2016 Prius and now 15,000 in my RAV4.

I was a devoted lover of ordinary CC since getting it in a Volvo in 1997 and once I experienced the Lexus ACC it was one of the features I wanted more than almost any other.  It was a key factor in my decision to replace a perfectly good 2012 Gen 3 Prius in 2016 with the Gen 4 (along with the safety sense features).

Personally, I use ACC a lot, even in town speeds (and especially in 20 limits) and even let it do a lot of my accelerating by hitting resume at low speeds or even while stopped.  Having said all that, I keep very close attention to surrounding traffic and am always ready to take over.  I've had no difficult situations to date (touch wood, of course), although I do agree there are times when it fails to detect a car in front for reasons it's hard to fathom.

By staying in ECO mode the acceleration when it briefly 'loses' the car in front on a bend (it reacquires when I steer which seems to affect the way the radar sensor is looking) the acceleration is minimal and manageable.  I also have to look out for the Lane Assist system trying to follow a car departing in a slip lane !  It's interesting how, when accelerating using ACC from low speed to high speed, switching though Normal and Sport modes ramps up the acceleration, the latter being pretty brisk.  The ordinary CC in the Gen 3 Prius didn't take any notice of which mode was selected.

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I too use it for many hours a week along with lane keeping, my only annoyance is it seems over cautious, in that on the motorway even if set to medium or short range and you start to catch up on a slower vehicle a long, long way ahead the car starts easing off way too early - it feels like it will take forever to catch up and close to the set distance. I want it to close up a fair bit quicker so I can then overtake without having to pull out quarter mile before the car ahead.

I don't use it on urban roads.

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My PHEV RAV 4 has Lane Tracking Assist.  To be honest it’s early days yet but testing it out today on the motorway was frustrating.  It wants to centre the car in the lane, which is fine, but seems to have a bias towards the left lane.  It has a tendency to sway and creates an uncomfortable ride, as if it’s hunting.  (Centring and over compensating and then moving the other way)  As I’ve said early days and I need to do a lot more testing and see if there are any settings to change the sensitivity?

It could also be me moving t he stealing back and the system then trying to compensate for me!

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59 minutes ago, ernieb said:

My PHEV RAV 4 has Lane Tracking Assist.  To be honest it’s early days yet but testing it out today on the motorway was frustrating.  It wants to centre the car in the lane, which is fine, but seems to have a bias towards the left lane.  It has a tendency to sway and creates an uncomfortable ride, as if it’s hunting.  (Centring and over compensating and then moving the other way)  As I’ve said early days and I need to do a lot more testing and see if there are any settings to change the sensitivity?

 

My experience of this is similar to yours - I'm not quite sure how useful it is to have Steering Assist on which is the default. Without steering assist Lane Tracing will warn you if you drift over lines without indicating which to me is adequate. This can be changed in the settings menu - quite a lot of info there when you find it !.

My other concern is that is fine the car staying in the centre of the lane as long as everyone around you is doing the same. I was overtaking a lorry on the M6 when a side wind blew him over towards my car - then I wanted to be away from the centre !

As for the original question, yes, I find the adaptive cruise control superb. You just have to watch for it sensing something like a slow moving lorry and plan when to move out. The warning on the 4.5 appears to me to be a lot smaller than it was on the 4.4 where it appeared large in the display and warned the driver.

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I also found the position was alarmingly close to the left hand side.  It is, as said, blind to a truck in the left hand lane not itself lane centred. I agree with its apparent tendency to hunt but check the lane guidance display.  It shows the lane confidence arrows with double blue being good and a single arrow, a blue arrow or no arrow show lesser confidence.  Informative as it may be, that is NOT where you should be looking as the low confidence will be when you should be concentrating in your own driving.

I have however, on a quiet road, tried to let the lane assist do all the work.  I have just touched to wheel to keep lane assist working and it does a reasonable job even on gentle bends.

One gotcha I have found with ACC is when the vehicle in front is approaching its turn off and starts to slow.  The ACC slows my car properly unless I signal to move out which is not always an option, so far, so good.  The problem arises when the car ahead either turns ( increasing its aspect and rapidly reducing its relative speed) or has left my lane and entered the slip lane, the ACC continues to brake and even increase the braking.  For the car behind it sees the road clear ahead of me and does not expect me to go into rapid braking and slow accelerating.

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I love the ACC, have no problem with it. In fact going round, for example, country road bends it is very useful. Say I set it at 45 mph and approaching a bend in the road not familiar with.  As I approach the bend I will flick the cc lever forward (temporary disabling), this rubs off a bit of speed by which time I into the bend. I then flick the cc lever up to resume set speed (ie 45mph). What this does is - put drive to the front wheels but not increasing speed whilst still in the bend. When exited the bend then the car speeds back up to 45 mph (assuming no vehicle in front). Of course if the bend is, for example, a long bend and I feel it would be safe to accelerate through it I can do.

in some areas ie 30 and 20mph max I set the speed control unit and therefore in full control of everything up to the max speed as set.

 

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CL, that is exactly how I used to drive in the Merc.  With the Corolla I find the CC Control is awkward requiring 3 button presses to engage and set speed the first time.  I am still learning the best way to do as you describe.  The other issue I have is the 3 presses are all on one ring with no feel for which you are pressing.  Many is the time I have pressed the OFF when I meant to press RES.  

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7 hours ago, Roy124 said:

...  The other issue I have is the 3 presses are all on one ring with no feel for which you are pressing.  Many is the time I have pressed the OFF when I meant to press RES.  

Yup!  Toyota are experts at 1 step forward, dozens back.

Previous Toyotas and Lexus used  a stalk for CC which was easier to use by feel alone.  The buttons that now do CC used to do what the buttons on the left of the steering wheel now do. I'm still sometimes messing up CC when I want to change the display!

Also, there are these backsward steps compared to my previous (older  cheaper) Prius Excel, which had:

  • all four window switches illuminated  and those on passenger doors
  • a more ergonomically designed switch layout on the driver's armrest, on the RAV I keep knocking the mirror fold switch to closed when shutting the door
  • mirror adjustment control was a large knurled knob that twisted to select left/right and was easily found without looking
  • roof switches that were easy to find by feel and also illuminated
  • illuminated glovebox
  • "rain repellent" front side window glass that was surprisingly effective
  • sound deadening laminated front side windows - I didn't appreciate how useful these were until I got the RAV that doesn't have them and hear a bit of wind noise from the mirrors at speed and more noise from diesels and cars with thumping music in traffic queues
  • a Head Up Display of speed and Hybrid System Indicator - a major safety aid that has been on the Prius for 10 years now
  • wireless phone charger (that's why I bought a new phone!  Grrr)
  • the best self parking system I've yet seen, made parallel parking in particular a quick affair as once selected it advised every time one passed a space the car would fit into (and could get you back out too)
  • a poor SatNav but at least it didn't revert to North Up every other time the car was started and numerals were on the same screen as alpha characters when inputting addresses
  • ability to use Playlists on USB music
  • 2 rear fog lights
  • Fewer information screens for mpg etc
  • Poorer quality speedo displays
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While we are on switchology, on the Corolla there is an EV switch, nkn-tactile on the gear shift console.  More often than not the computer finds some reason not to select it.. 

The very useful brake Hold button has to be selected EVERY TIME  you start the car.  Why? It's also out of sight line and I never remember until the first time I stop. What if I forget to operate it and assume I have?  Yes, I have done that. 

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9 hours ago, Roy124 said:

CL, that is exactly how I used to drive in the Merc.  With the Corolla I find the CC Control is awkward requiring 3 button presses to engage and set speed the first time.  I am still learning the best way to do as you describe.  The other issue I have is the 3 presses are all on one ring with no feel for which you are pressing.  Many is the time I have pressed the OFF when I meant to press RES.  

Totally agree on this, I don't think the media button should be on the same side as the driver aids either, I often try to change something by feel and end up accidentally changing the media source and get a blast of Long wave static out the stereo instead.

Too many button presses to set for functions. I once test drove a CR-V and you could engage the powerful lane keep function with a single button on the steering wheel and didn't need to have cruise engaged first like on the RAV, it meant you could use it much more frequently to give yourself a slight rest while controlling speed yourself.

Talking of the lane assist, I am surprised some have said its troublesome, perhaps their calibration needs redoing as I know the optics have to be precision aligned and software calibrated and even windscreen changes can mess it up. Mine works really well, keeps centre lane spot on, counters a fair bit of side wind very well too, only struggles on some wet roads with low sun making lines virtually invisible.

 

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I have a 4/RAV4 with the cruise control on a stalk.  I will comment on two difficulties I have had to get used to and be aware of.

If you want to reduce the speed by 5mph (or more increments) and press the stalk down the brakes are applied quite harshly and you must be aware of who is behind to prevent a rear shunt.

The stalk moves fully with the rotation of the steering wheel, and you have to be aware of where it is if you are driving on a road with frequent bends.

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My lane assist works well most of the time but our road markings are on a par with potholes and often invisible. Aside from the various edge displays, white arrow, hollow white arrow, white arrow and blue arrow, I occasionally get a white dashed line on the centre. Not quite sure what it means, very infrequent. 

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1 hour ago, Roy124 said:

...I occasionally get a white dashed line on the centre. Not quite sure what it means, very infrequent. 

It means it's using the radar and/or screen camera to follow the vehicle in front rather than just using the camera to 'see' the lane edges to guide the car.

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2 hours ago, gavioliuk said:

I have a 4/RAV4 with the cruise control on a stalk.  I will comment on two difficulties I have had to get used to and be aware of.

If you want to reduce the speed by 5mph (or more increments) and press the stalk down the brakes are applied quite harshly and you must be aware of who is behind to prevent a rear shunt.

The stalk moves fully with the rotation of the steering wheel, and you have to be aware of where it is if you are driving on a road with frequent bends.

Sounds like Prius has a stalk and functions like you 2019 Rav.
I find reducing speed using the stalk just by 5mph is not really aggressive, flick it twice to reduce 10mph, yes, it gets more aggressive. I can always brake (or indeed accelerate).

Yes, my stalk moves with the steering wheel, I am used to it now, if need be I can brake gently/harder as I deem fit for the circumstance, or accelerate. 
I don’t allow those aids to take control, I am in charge, and I have got to know their quirks.

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23 minutes ago, PeteB said:

It means it's using the radar and/or screen camera to follow the vehicle in front rather than just using the camera to 'see' the lane edges to guide the car.

Thank you Pete, good to know.  As I routinely use the '3 car' space setting I may be out of 'follow me' range and only get that when a car pulls close in front until the spacing increases again.  I will watch how it displays next time.  

I had one very relaxing drive not long after I got my car.  I was following another car at a comfortable speed and it was obeying all the Eco rules.  The car inI had to do nothing except steer.  Only towards the end and we were close I saw it was another Toyota Hybrid.  On another occasion lane assist had me following a truck into a filling station!

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1 hour ago, Catlover said:

Sounds like Prius has a stalk and functions like you 2019 Rav.

Yes, sounds like William has one of the last of the 4th Gen RAV4s which had the stalk.

The 5th Gen (launched in 2019) has the buttons where your display control buttons are one the right side of the steering wheel, and from what I've read the latest Corolla has the buttons too.

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2 hours ago, PeteB said:

Yes, sounds like William has one of the last of the 4th Gen RAV4s which had the stalk.

The 5th Gen (launched in 2019) has the buttons where your display control buttons are one the right side of the steering wheel, and from what I've read the latest Corolla has the buttons too.

Yes I took delivery of my 4th Gen in March 2019 at a good price and 3 years at 0%.  The dealer claimed it was the last 4th Gen to be delivered in the UK.

1st Toyota after 50 years of Fords from the same salesman, following round several dealerships.  So pleased we made the change.  Problem is my wife loves driving it, whereas before she hated driving.

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