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How would you drive the following typical segment?

Stopped at a red light, accelerate up to some speed, drive for a "while" then decelerate at the next red light.

Say the following is the case:
- Light traffic
- 45mph speed limit between the lights
- Assume you will be stopped at the next light
- SoC ok at say 6 bars
- Car warmed up
- Level ground
- Next light is 1/2 mile away?
- You are in an HCH2....

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How would you accelerate?
What would your target speed be?
When would you start to decellerate?
How would you decelerate/come to a stop?
Other considerations?

How would this change if traffic, the speed limit, distance to the next red light, or make of hybrid changed?

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Ill start things off (right or wrong, its what I tend to do)
1. Accellerate at 1.5-2k rpms until maybe 35mph (I dont like driving too far below the speed limit)
2. Back off throttle until all assist bars dissapear (maybe a regen bar appears) then hold throttle there
3. See if light ahead is probably green - if so, accellerate up to about 45mph.
4. Since light will be red, just glide with no regen and hope speed bleeds off...
5. If speed not bleeding fast enough - like still above 30mph and approaching light, will lift foot off throttle altogether or even drop down from D --> S to get some more regen. Still trying not to press brake pedal.
6. If still going too fast, may go back into D and depress brake until stopped.

Interesting question!

If I *knew* I couldn't coax that next one to change somehow, I'd probably do the following:

- Accel up to maybe 35 (one of the assumptions was light traffic, I'm also assuming a 4-lane road so I could stay out of the way of what traffic there was... otherwise top speed might need to be a little higher). "Normal" but not heavy acceleration. In the prius the rate of acceleration doesn't matter so much, but shoot for getting some battery charge out of the "pulse".
- Glide/fas/neutral/DWB up to the light depending on your car, the legality of using neutral, your comfort with FASing

My experience is that the lights are often timed so that if one turns and you were to get up to the speed limit 'normally', you would still have to slow down before the next one changed. With a peak speed of less than the speed limit, you can let everyone else do that, get the light to change still before you get to it, and give the 'rabbits' enough time to clear out so you can glide through the light.

With lights spaced 1/2 mile apart, 70-80% of the speed limit seems like a good top. With NO traffic I'd be way more "aggressive" and shoot for maybe 50-60% until I was convinced the light was timed sanely and would actually change before I got to it. If there were more lights later on I'd then get closer to the speed limit to catch them all in the middle of their greens. :D

On a 2-lane road with pedal mashers behind you, or heavier traffic, you might have to bite the bullet and drive "normally". Doesn't mean you still can't sneak in a glide and start slowing down earlier, but your top speed may need to be higher.

My suggestion is to try another route. :)

I have a similar situation on my commute, and I'm trying to figure out a way to mitigate it. EV-only is too SOC expensive, and I lose a guaranteed 5-10%mpg every time.

Reds close together are not our friend.

Thanks - should have mentioned that I am in an HCH2...

But the tips seem to apply to both Prius and HCH2.

How would you drive the following typical segment?

Stopped at a red light, accelerate up to some speed, drive for a "while" then decelerate at the next red light.

Say the following is the case:
- Light traffic
- 45mph speed limit between the lights
- Assume you will be stopped at the next light
- SoC ok at say 6 bars
- Car warmed up
- Level ground
- Next light is 1/2 mile away?
- You are in an HCH2....

------------
How would you accelerate?
What would your target speed be?
When would you start to decellerate?
How would you decelerate/come to a stop?
Other considerations?

How would this change if traffic, the speed limit, distance to the next red light, or make of hybrid changed?

-------------
Ill start things off (right or wrong, its what I tend to do)

My 2 cents in red

1. Accellerate at 1.5-2k rpms until maybe 35mph (I dont like driving too far below the speed limit) If it's light traffic, what's the rush. I'd go no higher than 30, hoping the next light will change by the time I get there
2. Back off throttle until all assist bars dissapear (maybe a regen bar appears) then hold throttle there check
3. See if light ahead is probably green - if so, accellerate up to about 45mph. If green, I'd accelerate VERY slowly to 40 (max) while holding the ifcd at 50 or greater
4. Since light will be red, just glide with no regen and hope speed bleeds off...If I "know" that light's going to be red I don't give it any more power than I need to glide to a stop.
5. If speed not bleeding fast enough - like still above 30mph and approaching light, will lift foot off throttle altogether or even drop down from D --> S to get some more regen. Still trying not to press brake pedal. If next red light is unexpected, I just eat all the regen I can, if nothing else I can do. But hold off braking long as possible.
6. If still going too fast, may go back into D and depress brake until stopped.


Your red light situation reminds me of the classic trade-off I'm constantly making in my head about which is worse --coming in too hot and have to brake, or coming in too slow and have to speed up? Answer is yes

Good stuff - thanks.

ACCELLERATION
- When getting up to target speed (30,40....) is there a max rpms or assist bars you try to stay below?

DRIVING
- Say the distance between the lights is 1-2+ miles instead of 1/2 mile. Would you set your target speed differently? Not just because you dont want to come into the next light "too hot", but perhaps there is a target speed that gives better FE for the 1+ minutes you are at this speed?
- Which speed gives highest FE - 20,30,40?
- Put another way, is there a target speed - say 40mph which gives better SEGMENT FE than 20mph even if it is less efficient at Accelleration and Decelleration/stop? At the extreme, I suppose a 100mile trip (between lights) would be run at some target that gives optimum FE adn that the acelleration and decelleration would be relatively insignificant in this case.

DECELLERATION/STOP -
- Try to keep any regen bars from showing up as long as possible on the glide?
- Then try not to hit the brakes at all after that (other than to do autostop at 8mph)?
- If you are still coming in too hot, do you ever drop it into S from D or just let off the throttle?

...

Say the following is the case:
- Light traffic
- 45mph speed limit between the lights
- Assume you will be stopped at the next light
- SoC ok at say 6 bars
- Car warmed up
- Level ground
- Next light is 1/2 mile away?
- You are in an HCH2....

------------
How would you accelerate?
What would your target speed be?
When would you start to decellerate?
How would you decelerate/come to a stop?
Other considerations?



I drive 100% under those conditions and wether it is the HCH or the Prius, it is always a bit of a challenge. Also, I guess much depends on what our assessment of the accompanying traffic around us is, in addition to what's ahead.

How would you accelerate?
If there's traffic behind: On the HCH-II I accellerate briskly preferably staying below 2500 RPM. Once I reach my target speed I simply glide to the stop. I make sure my glide is as long as possible. I use EV only if the road grade allows minimal EV and maximum distance covered. Same thing on the Prius.

If there's no traffic behind: On the HCH-II, I accellerate smoothly keeping the rpm close to 1000rpm and I minimize the assist/ev as much as possible especially if the next stop is much less than half a mile away. On the Prius I have no such concern but I still hate having to do deplete the rather expensive SoC in frequent slow Stop & Go. On both, I have the scangauge on LOD (engine load) just to get an idea of what the engine is really doing. The iFCD on the HCH-II does not appear very accurate at low speeds since it seems to over-report.


What would your target speed be?
If there are no cars ahead of me my target speed is perhaps a bit higher than the speed limit (5 o 7 mph). If there are no cars behind me my target speed is quite a bit lower then I glide the rest of the way to the stop.

When would you start to decellerate?
I start decellerating more in a form of a no regen glide as early and for as long as possible. If I have to slow down more aggressively I try to get as much regen as possible without maxing out the regen bar scale.

How would you decelerate/come to a stop?
Smooth as possible, hopefully done in such a way that I may not have to come to a complete stop at all. No regen it at all possible.

Other considerations?
As mentioned, for me traffic intensity as well as road grade play a very import role. I figure them to be just as important as the timing of the lights and engine temperature.


Cheers;

MSantos

Thanks all - great advice! What I read was:

Seems like at start, keep rpms <2k unless traffic is really pushing you to 2.5k or so.

If traffic really light, target under the speed limit. If you want to be at the speed limit, pulse to about 5mph above then glide down.

Let "rabbits" run ahead a try to trip the light back to green.

If you have to bleed off speed quickly, 1) try not to use brake and 2) try not to max out regen bars.
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** If possible, find other routes avoiding these situations. Maybe I should start timing/logging the actual green/red cycle times for the 13-14 lights I pass on daily commute to work.

Q - Scan Gages useful in HCH2? Easy to mount/install? What key info do you tend to use from it?

Best regards,
Carl

** If possible, find other routes avoiding these situations. Maybe I should start timing/logging the actual green/red cycle times for the 13-14 lights I pass on daily commute to work.

I've been wondering - and doubting whether - the scanguage has a "fuel used this trip" display. Because I wonder if people are always considering that a route with higher FE may be one that uses more gas. I'm not suggesting that's your case in particurlar, Sparty, just haven't seen this addressed yet, though I am "green" on this green site. Comments/concerns?....

I've been wondering - and doubting whether - the scanguage has a "fuel used this trip" display. Because I wonder if people are always considering that a route with higher FE may be one that uses more gas. I'm not suggesting that's your case in particurlar, Sparty, just haven't seen this addressed yet, though I am "green" on this green site. Comments/concerns?....

There is indeed a tally of fuel used for the current trip. I know that for example I typically use 0.5g on the way to work, and 0.6-0.7g on the way back (depending on traffic and route). If I had unimpeded driving in the afternoon I know I could get the usage to equal and maybe even get lower than the morning drive (I'm on the road at 5AM so traffic usually isn't much of a concern, really), but traffic determines the trip time. In my case, I take a longer route home that doesn't require me to stop and idle as much -- I use less fuel that way.

Q - Scan Gages useful in HCH2? Easy to mount/install? What key info do you tend to use from it?


You can get a fair amount of info from it but saddly, none of if is direct hybrid info.

Still, the info you can display is pretty useful since it can tell much about the ICE and it also extends the Trip functionality of the HCH-II & Prius.

I have my Scangauges set to display 4 values simultaneously:
- LOD (Engine load)
- System Voltage
- cAI (Air intake temperature)
- cWT (Coolant temperture)

Mounting the unit and using it on an HCH-II is easy, picking a good location for it depends on your enginuity and taste. I mounted mine on the center console between the shifter and the cup holder with some adhesive velcro strips.

Cheers;

MSantos

I've been wondering - and doubting whether - the scanguage has a "fuel used this trip" display. Because I wonder if people are always considering that a route with higher FE may be one that uses more gas. I'm not suggesting that's your case in particurlar, Sparty, just haven't seen this addressed yet, though I am "green" on this green site. Comments/concerns?....

Yes, cycle through the trip totals and you will see gal used. Unfortunately for shorter trips it's practically useless since it's only accurate to 0.1 gal (I don't often show over 0.2 on any given segment in my daily grind). Is it too much to ask to show in oz or even ml? :D

(Yeah, I know it's not directly measuring fuel consumed but more of an approximation based on air intake... that's why EVing around a parking lot you will see some absurdly high trip MPG - but not maxed out/infinite. Maybe oz or ml wouldn't be much more accurate after all. I can hope anyway. ;))

You can get a more accurate sense of fuel used by taking your trip distance and dividing it by your trip MPG. To see what MPG you'd need to get on a longer trip to use the same amount of fuel, you can do this:


shorter trip dist longer trip dist
----------------- = -----------------
shorter trip MPG X


=>

X = (longer trip dist) * (shorter trip MPG)
-------------------------------------------
shorter trip dist

As an example, if your shorter trip was 5 miles and you could get 40MPG, to use the same fuel for a trip of 7 miles you'd need to get (40*7)/5 = 56 MPG.

My suggestion is to try another route. :)

I have a similar situation on my commute, and I'm trying to figure out a way to mitigate it. EV-only is too SOC expensive, and I lose a guaranteed 5-10%mpg every time.

Reds close together are not our friend.

I'm in Austin too. I think there is a potential to save thousands of gallons of fuel in this city by just working out the lights. It never fails that when you get up to 70MPH on roads like 360 the light will turn red to let ONE car go through the intersection. There are times when I leave work the car will idle for 3+ minutes trying to get across Parmer.