Traffic Jam Assist?

I find it very useful. It moves the car along with traffic, keeping the car in the lane and avoiding other cars.

I don't like the way it engages/disengages on its own. I've never found a way to activate it myself. Also, it keeps asking if you want to consent to being recorded. I can't think of any benefit to that, so I always refuse. It stopped happening when I found a way to disable the DMC (driver monitor camera) in the setup.

 

It will turn on automatically if the following conditions are met:
- You have an active Drive Connect subscription
- You are driving less than 25mph(or thereabouts)
- You have Adaptive Cruise Control on and set
- You have Lane Tracing Assist on
- There is a car in front of you
- The cameras on the steering column can see your eyes
- I think you have to agree to being recorded, but I'm not 100% certain on this(the regular Prius doesn't have TJA, so I haven't used the system myself to test)

If all these conditions are met, the system will activate automatically. You can't force it on. Once it's on, it will shut off automatically(after giving you a warning) if any of these conditions are no longer met.

I believe the TJA section in your manual starts on pg 348.

 

It sounds like improved cruise control that doesn't auto turn off at full stop. Does it auto lane-changes? Probably not.

 

The only differences I can see between Adaptive Cruise Control and Traffic Jam Assist is that the car will accelerate from a dead stop on its own and you don't need your hands on the steering wheel for it to function. ACC doesn't need to be reset after a full stop, but you have to initiate the acceleration with the pedal. You also need to either have your hands on the wheel(PHEV) or give an input to the steering angle sensor(HEV&PHEV) every 15sec for it to continue to function.

It can't decide to lane change on its own, but it will perform a lane change(if safe) if the driver commands it by partially pushing the turn signal lever for two or three seconds(Lane Change Assist).



Differences between the PHEV and HEV safety systems and what those changes mean:
1. PHEV has the capacitive touch steering wheel
2. PHEV has front side radar(required for Front Cross Traffic Alert, Lane Change Assist, and Traffic Jam Assist)
3. PHEV has driver monitoring system(required for Traffic Jam Assist)

Any HEV can add the capacitive touch steering wheel easily. A Limited with the Adv Tech Package can physically add the front side radar easily, but the programming of the new sensors is proving to be a nightmare due to a bug in Global TechStream. All other HEVs would need to add wiring to add the radar plus still have the programming problems. I suspect you could add the driver monitoring system to a HEV, but it probably means pulling the dash, and I don't know how easy any programming would be.

 

The only other thing I can add, per the Owner’s Manual, is that Traffic Jam Assist (TJA) is only available on "some highways and expressways".

That restriction finally made sense as to why TJA requires an active Drive Connect subscription. Since Drive Connect provides Toyota’s cloud-based navigation and real-time traffic data, it also provides Toyota with access to your vehicle’s precise location, which in turn lets Toyota determine whether you're on a TJA-approved roadway.

 

In my Gen 4 PHEV, it is a capacitive sensor on the steering wheel.

 

I don't find myself on highways where the feature works but I did have a chance recently. The biggest difference I noticed between regular ACC with lane centering and ACC with TJA is I don't need to have a hand on the steering wheel while it's active (under 25mph). It still needs baby sitting to keep it active where the speeds are right around that transition between regular ACC and TJA. hands vs hands off. Because if my limited use of roads where I can use the feature I'll most likely cancel it once my free trial is up.

 

I got a subscription for one month and found TJA is of very limited benefit, unless you drive in a lot of bumper to bumper traffic jams. The Toyota navigation is inferior to Google maps, especially the voice commands.

 

I have found it useful. I do not regularly sit in traffic but it makes navigating stop and go traffic less stressful. Going from memory you do not need to consent to being recorded for it to work. I am pretty sure the recording is used for Toyota to make improvements to the system. If you take you hand off the wheels for somewhere about 30 seconds you will get an alert warning you Traffic Jam Assist will turn off. You can pinch the wheel and the message will go away.

From my own user experience I don't think you always get the animation when TJA is in use. I notice the notification more when I am using adaptive cruise control at regular speed and traffic slows down. I am pretty sure if you are using adaptive cruise control when traveling at speeds below 25 mph you are essentially using traffic jam assist.

It does not sense traffic signals or stop signs so if you are on a highway with traffic and the light turns red you will need to break in order to not run the light. I am pretty sure that it is always the case that if you car has come to a complete stop in traffic you will need to initiate acceleration once traffic has started moving again by pressing the + button. This took me some time to get used to this and remember to keep my thumb on the button.

Although not a part of TJA I do use the Lane Change Assist pretty regularly when driving on the freeway. I haven't had any issues with it approving of a lane change when there was a car next to me.

I am currently playing with the Predictive Efficient Drive feature and how it is integrated with the navigation system. The user interface is not all that intuitive for the built in navigation assist but I have noticed recently by putting my destination into the Toyota navigation system I can use more of the battery charge at higher speeds where without inputting a destination in the gas engine kicks in.

 

If you're needing to press the resume button, that shows you're not using TJA, it's just the base DRCC. There's not a huge functional difference, as Hammersmith noted above.

But making it autonomous enough to not require any driver input presumably adds a whole bunch of conditions. Including it being on a freeway and knowing the road in navigation.

You are thinking of the Predictive EV Drive subfunction, but I believe that still isn't present in US cars, and your description doesn't quite tally.

I don't think entering destination in a US car will change behaviour.

I wrote about the function here:

Predictive EV drive experiences | PriusChat

We don't get TJA in Europe, so everyone misses something (except the Japanese?)

 

When I was new to the car, I initially believed I might have been in TJA mode myself at times when it was still just DRCC with LTA. That confusion came from an initial read through the owners manual about DRCC being available at 20 mph or higher and TJA being there below those speeds. But turns out you can enable DRCC at less than 20 mph if you are following another vehicle. I use it quite often on some surface streets that would never be TJA approved. But even DRCC with LTA allows me to take hands off the wheel for quite a while and it'll automatically brake and even resume automatically but only if stopped for an admittedly short time (seconds). But, like otatrant mentioned you just press the resume+ button to move with traffic again (where even the nice led light accent across the dash flashes when the car you are following moves forward).