I've been waiting to try this out and over the weekend, I got caught up in some fairly light traffic. I must say that I don't like this feature at all. It performed braking way too early and harshly, which in my opinion is more dangerous. I'll try it out again of course, but not impressed with first-time use here.

 

There are sensitivity settings in the head unit you can adjust. Here is a long video of the system functioning in an NX:

 

I think that this video is different than what we have on the 23 RX…which is completely hands free when conditions are met. I have several hours now with adaptive cruise and traffic jam assist, on an interstate highway it works well and reduces driver workload, stress and fatigue. It does not handle sharp curves i.e over 45 degrees but for the most part works well. I’m curious what the system functionality is when the subscription runs out?

 

After the free 3 years, if you don't renew the subscription you basically have a $620.00 white elephant.

 

When the "conditions are met" , does adaptive cruise need to be engaged for "traffic Jam assist" to work and does it engage automatically?

 

Probably nearly all of the $620 is the cost of a 36 month subscription. Can't seem to find what they'll charge though after the 36 months.

 

It's part of the "Drive Connect" subscription, isn't it. It was never clear what the system actually stops doing when the subscription runs out. I don't see why it needs cellular data to operate, its just using the cameras and the sensors to pace the car in traffic, stop, go, follow, lane keep, etc.

 

According to the Technical Specialist at my local Lexus dealer whom I spoke with just a few days ago on this topic, Traffic Jam Assist will engage automatically under the right conditions, provided that Adaptive Cruise Control is operational. There is no button to turn it on/off.

See page 275 of your Lexus RX full manual:

 

Think of it similar to additional dealer markup, but instead of door sills or nitrogen in your tires, you get something more useful.

 

Not useful for me. It has not engaged once. This is additional MANUFACTURER markup.

 

Have to say I really like it. Works seamlessly for me so far. In stop and go traffic I have it set for two carlengths and no issues. It will come to a complete stop and then start again.

 

Not useful to me. I pretty well know where the traffic can be found at most times of the day.

 

It’s a semi self-driving-in-traffic thing. Not something to tell you where to avoid traffic.

 

The Lexus implementation of "auto-drive" is pretty good and most importantly quite useful. Consumer Reports has several articles on the technology and rates the various manufacturers. They don't consider Tesla's implementation to be safe as there is no driver monitor system. I don't think that consumers understand all of this yet and the safety standards / ratings have yet to be been articulated.
All of this will be standard soon, you won't even be able to option Traffic Jam assist in the future. I think that there will be a subscription charge that will be mandatory if you want "advanced" features that require internet connection.

 

This all may be true, but it has nothing to do with my reply to ggebhardt regarding his apparently mistaken notion that this option is something that finds and alerts you to traffic.