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I was driving on a motorway today where there were speed restrictions and plenty of traffic.
Decided to use Traffic Jam Assist and was pleasantly surprised how long I could drive hands free. I managed to get 9mins 47sec without any warnings or placing my hands.

Having thought about this, I suspect there are different set of rules for hands free operation of Traffic Jam Assist in motorways under low speeds. I was averaging under 10mph. What are your thoughts and experiences?

[DBO]

I recall in the MB we had, it stayed on indefinitely as long as speed was below 30km/h. I think it's similar in the BMW. I've had similar experience to what you describe. Can't recall reading about exact numbers though.

[AP]

Yes noticed the same. At low speeds the prompt takes longer to pop up although I haven't timed it myself.
As I've mentioned before Tja I think is the best (and arguably useful) part of the system , much more than lane assist.

[ADS-UK]

Originally Posted by DBO

I recall in the MB we had, it stayed on indefinitely as long as speed was below 30km/h. I think it's similar in the BMW. I've had similar experience to what you describe. Can't recall reading about exact numbers though.

Ah. It probably would have stayed longer if the traffic didn't ease up a little bit pushing me over 30mph.

I've also noticed that this only works if you in a Motorway environment than city traffic.

[ADS-UK]

Originally Posted by AP

Yes noticed the same. At low speeds the prompt takes longer to pop up although I haven't timed it myself.
As I've mentioned before Tja I think is the best (and arguably useful) part of the system , much more than lane assist.

Agree. TJA is definitely the most useful part of Driving Assistant Plus.

I wonder whether there's a chart somewhere that shows different conditions and timing you are allowed to be hands free.

[AP]

Not seen anything. Even the technical docs available on this website don't go to that level of detail.

I quite like watching the car steer itself as it follows the car in front on non motorway roads.

The other part of the technology I've not been able to find enough info is the evasion aid. Just feel the technical docs don't go into quite enough info to explain. Of course it's not something I want to try out for real!

I would love to be able to take a car (not mine) off road and explore these systems to see what the limits without worry about damaging mine.

[ADS-UK]

Originally Posted by AP

Not seen anything. Even the technical docs available on this website don't go to that level of detail.

I quite like watching the car steer itself as it follows the car in front on non motorway roads.

The other part of the technology I've not been able to find enough info is the evasion aid. Just feel the technical docs don't go into quite enough info to explain. Of course it's not something I want to try out for real!

I would love to be able to take a car (not mine) off road and explore these systems to see what the limits without worry about damaging mine.

Couldn't agree more. In fact I was thinking this morning about evasion aid. I was wondering how would you ever know if the system works as you'd never want to be in a situation like that

[AP]

Yep. Maybe I am being thick but just not 100% sure what the car is doing for you.
My take is that it knows what lanes are clea and if you suddenly swerve into that clear lane with traffic in your lane it will support you.( surely dsc will do that for you anyway??)

Just something you can't try out for real and hopefully never have to.

[bpbaud]

In the US, traffic jam assist disengages if you remove your hands for more than about 30 seconds, regardless of the speed you're traveling. Disappointing.

[AP]

Interesting so regional differences. The docs on this website support that but in the U.K. it is certainly more that, although the logic behind it is not clear but would appear to speed related.

I wonder if it is essentially distance related as well ?

I might ask my dealership if they have any info as I'm taking it in for a software update. Will present a copy of one of the docs here (US version) and see if they have a EU equivalent they would be prepared to give me.

(My car a July 2017 one is due a gearbox selector enhancement fix , whatever that is. Have also asked if they can apply the sib for the a/c. Wonder if this will result in a complete istep upgrade. )

[ADS-UK]

Originally Posted by bpbaud

In the US, traffic jam assist disengages if you remove your hands for more than about 30 seconds, regardless of the speed you're traveling. Disappointing.

It is also dependent on the road. Logic would say motorway environment in low speeds are relatively safe to let TJA work. Maybe there are some regional regulatory challenges.

[Rob500]

Originally Posted by ADS-UK

Agree. TJA is definitely the most useful part of Driving Assistant Plus.

I wonder whether there's a chart somewhere that shows different conditions and timing you are allowed to be hands free.

I don't know about a chart but I've seen something that says TJA will work hands free for an extended time so long as you are going at less than 19mph and you are on a "highway". On ordinary roads or at higher speeds it only lasts a few seconds before wanting your hands back on the wheel. My experience in practice confirms that it works this way.

[ADS-UK]

Originally Posted by Rob500

I don't know about a chart but I've seen something that says TJA will work hands free for an extended time so long as you are going at less than 19mph and you are on a "highway". On ordinary roads or at higher speeds it only lasts a few seconds before wanting your hands back on the wheel. My experience in practice confirms that it works this way.

Yes, that's what the manual and technical docs say. I was wondering about the specifics. Maybe it works indefinitely if the speeds are maintained below 19mph?

[tompak23d]

I read about this in the manual for my car a long time ago. In lower speeds (don´t know how low) it follows the car ahead of you in combination with the line assist. Sorry for my bad English, I hope you understand .

[Rob500]

Originally Posted by ADS-UK

Yes, that's what the manual and technical docs say. I was wondering about the specifics. Maybe it works indefinitely if the speeds are maintained below 19mph?

Well as far as my experience goes it just carries on until you cancel it or the speed goes above 19mph. However, if you do come to a complete stop then it will only start moving again automatically for a relatively short while (but quite a lot longer on a "highway" than on an ordinary road) after that you have to tap the accelerator or resume button to get it to start up again.

[roadske]

From my experiences in Denmark, when it uses ‘follow car in front mode’ - whether or not in combination with lane assist - and the speeds are below about 30-40 MPH, it can go on forever without needing hands on. This has no bearing on being in city or highway, although the situation mostly occurs on highway queues for myself.

It’s quite nice - especially if you’re stuck in a large queue that can take 15-30 minutes to get out of. I haven’t timed it, but I will try next time.

And yes - documentation is poor.

I’ve had the car brake hard on 2 occasions when parking and got too close to something behind me, so nice that it works!

I also like the alerts you get, if you’re turning left/right, and it notices traffic around the corner - the red alert and audio notice is great! It’s radars are phenomenal here!

[ArchJR]

Originally Posted by bpbaud

In the US, traffic jam assist disengages if you remove your hands for more than about 30 seconds, regardless of the speed you're traveling. Disappointing.

The system always requires more patience in the U.S. since drivers here like to fill a gap just to get one car length ahead in traffic. I tried using TJA in suburban Miami traffic and could not make it a block without getting cut off.

[cartaozinho]

Originally Posted by ArchJR

I tried using TJA in suburban Miami traffic and could not make it a block without getting cut off.

California drivers seem to have attended the same driving school! Some people even like to weave in and out of freeway traffic like it's a Hollywood set. I wonder if they realize that the filming of chase scenes (1) involves professional drivers on a closed course, (2) are highly scripted, and (3) for safety reasons, occur at 20 mph, not 75. Although, I'm sure some people think the same of me when I zip by them in the outside lane on a cloverleaf...but the M550 just begs me to accelerate!

While on the freeway I make extensive use of the driving assistance features (LKA, ACC). But almost never on surface streets -- the system has a hard time with line breaks for turn lanes and when the white line goes missing at intersections. Plus, many roads here in California are poorly painted.

For freeway driving (but not freeway ingress and egress) I almost always have LKA and ACC active. For me, they make "low level driving processes" require less brain power. This lets me focus more brain power on "higher level driving processes" such as keeping an eye out for the aforementioned Need For Speed wannabes and other potentially unsafe situations. On the one longer trip I've taken in my Bimmer I noticed that I was much less fatigued at the end of a long day of driving. I attributed this primarily to the DA systems requiring less mental energy. Or maybe it was the massage seats!

Like others, I have found Traffic Jam Assist (TJA) to be fantastic. For some reason I have 37 mph stuck in my head regarding the maximum speed for TJA. And like others, that seems to fit my experience regarding latency of "hand on wheel" requests from the car. I don't know about others but for me, stop-and-go traffic is the worst part of driving. The TJA system does such a good job, though, that I hardly care about it any more.

In some respects I'm happy that the average driver doesn't have these features (yet!). My guess is that instead of the average driver using these systems as a tool to complement and improve their driving they would use them as a substitute which would worsen their driving. It's not hard to imagine many drivers just burying their head in their phone while letting the car drive along at 75+mph. These are driver assistance systems, not driver replacement systems!

[SteveinArizona]

One of the reasons I bought a 530e was to be able to drive in the HOV lane at any time of any day. But that means that I am never in the type of highway driving that provides for TJA. So I have never experienced it and I hope to never experience it (okay...once when I am not in a rush would be nice).

[ZigmundUK]

I have an x5 and the g30. Both have the driving assistant plus. What used to be called tja is now basically the same thing as auto cruise control and steering assist combined but at low speeds. In the f15 tja is pretty useless. It only engages on dual carriageways and at under 30 Mph. In the g30 the whole package is great. At high speeds you get 30 seconds of hands free max (about 23 of those are with warnings). At low speeds like op mentions there's no real limit.

Since there is no steering assist in the f15 I've come to realise how much I rely and like it in the g30. Took a long trip in the f15 and I really missed it.

[rudling]

Would be interesting to chase down whether there really are regional differences in the hands-free tolerance window. And if so, whether coding can alter the window time?

Any volunteers from the US and elsewhere to get some (additional) real-world data points?

[AP]

Difficult to measure in traffic as speed varies so difficult to work out the logic behind it.
In general it seems you get a longer time without being prompted to put hands back on at lower speeds but as I say not sure what the exact algorithm is.

As the traffic moves differently in every situation I guess it will be difficult to get a consistent measure.