Dynamic cruise control

On Saturday I drove 120 miles on the highway without touching the brakes. I hit traffic several times and followed cars several times at speeds slower than my set-points. I mostly used one bar at high speeds and 2 bars at slow speeds.

 

Do the bars set you at a distance or time gap? My current car leaves 2 seconds gap on cruise control. This means the gap grows as the speed increases. Is this the same for the Toyota system?


iPhone ?

 

I think it's a combination. It's definitely not a fixed time gap because that would mean zero distance at zero speed. But the distance definitely increases with speed. It's probably something like 10 feet plus 1.5 feet/mph, changing with number of bars.

 

Does the manual give and clear answers?


iPhone ?

 

So if my model is correct:

Long = 16 feet + 2.88 feet/mph
Medium = 16 feet + 2.28 feet/mph
Short = 16 feet + 1.68 feet/mph

 

related question to the DRCC: when it engage and slows you down, at what point, if at all, do the brake lights come on?

 

I didn't check, but I would presume the brake lights come on any time it has to use a level of braking higher than the equivalent of letting off the accelerator pedal.

And by the way, it will use more than that just decending a hill with no one in front of you.

 

from th manual pg 395:
edit: it's not taking my screenshot ...
When a vehicle is detected running ahead of you, the system automatically decelerates your vehicle. When a greater reduction in vehicle speed is necessary, the system applies the brakes (the stop lights will come on at this time).

 

found the answer in the manual ... not sure i understand your 2nd point about decending?

 

If you go down a hill that, without cruise control, would cause you to accelerate without your foot on the pedal, with cruise control, it won't accelerate because it will apply additional braking.

 

yes, correct, thanks for clarifying. One of the areas i have to re-learn with the Prime: in my Gen3 Prius, when descending i had the gas pedal at the "sweet spot" to ensure no energy flow (no charging, no fuel into the ICE) and I reached speeds of 80+ on some of the hills on my daily commute. With the Prime, I set the CC and regain EV range. I need to do some profiling and start a log to understand all the differences.

 

I love it! And yet I still am a bit apprehensive when its on. I share this for anyone who doesn't have the car yet and wants to understand what its like. When you turn on cruise control, the DCC is active. If you are going less than 28 MPH it sets itself to 28, but will be active. It will come to a complete stop behind a car, and in most instances you will either need to tap the gas or press up on the cruise stalk to start following again. If your complete stop to zero is less than about 2 seconds, it seems to resume fine. You can increase/decrease your set speed while it is dynamically following another car and it will maintain speed and only use the new speed once the road ahead opens up. I only ever use it in Eco, and I find that its acceleration after a car moves out of the way is sluggish, but I assume that's for gas savings. Like someone above I have had lots of cars cut me off and it reacts, but maybe a bit slower than I am comfortable with. (I wish it had some type of indication of cars in other lanes it shared in the dash) The distance buttons feel rather insignificant in differences. I generally use 1 in heavier traffic just to seem more "normal" and 3 at all other times.
I commute from Emeryville CA to my home in Vallejo CA every day in some of the worst traffic I have ever experienced, and this car has reduced my stress and exhaustion probably about 50% there is an amount of inattentiveness you can have that really makes driving that much more calming. It also follows cars through the toll plazas quite well.
Really the only time I scare myself is changing lanes to take an exit, and forgetting that my set speed is much higher than the following speed I was going at so the car begins to accelerate as I am making an exit, but that is easily remedied by hitting the brakes, just something to note. It can't do all the driving yet!

 

On previous generation Prii with regular CC, not DRCC, there is plenty of cruise control braking at a level higher than the equivalent of letting off the accelerator pedal, in the form of electrical regeneration for battery recharging, and engine compression braking equivalent to downshifting a traditional non-hybrid. Neither of these paths turn on the brake lights.

Based on that, I wouldn't accept 'I would presume the brake lights come on...' as a useful answer, but would insist on other evidence.

The other answer, from the manual, is more specific. If it needs to apply the brakes too, then the brake lights turn on. But be aware that there is a significant amount of braking available without using the actual brakes.

 

Not on my 2004.

 

@joachimz answered this earlier in this thread.

 

There was on my 2010, and still is in my 2012. I use this feature occasionally on downhills too short to need B mode.

And addressed in my last paragraph. But in particular, don't miss my last sentence there:

I.e. significant braking, more than D-mode release of gas pedal, without lighting up the brake lights.

 

re-gen is definitely much "stronger" in the Prime vs Gen3 Prius, so understanding when brakes are applied (e.g. brake lights coming on) would be helpful. I use CC a lot, even within city going 40mph and in my Gen3 i've used it e.g. approaching a red light and it slowed down gently, in the Prime, when e.g. CC is at 50mph and i click it down to 40mph it feels like braking but i am almost certain it is NOT using the brakes. Maybe i need to take a drive in the dark where i can see the brake lights coming on in the rearview mirror to understand the behavior ...

 

Just got our Prime a few weeks ago, and I agree with Joachimz - I'm also a bit nervous when CC is engaged and I'm cautious when trusting this new technology to keep me from hitting the car in front of me . It works great (gotta have faith, but NOT TOO much faith according to the owner's manual!). Only peeve is that cars in adjacent lanes see the large distance between me and car in front of me (thanks to the CC) and jump into the gap in front of me. This triggers the CC to slow down my car, then allowing more cars to jump into the gap in front of me. I should say I'm driving in heavy traffic in So Calif, so the driver behavior described is not indicative of all folks! But it's really reassuring to read the good stories of avoided collisions and relaxed driving on this forum using the radar-controlled CC!