using "park" at red lights?

You won't have any mechanical issues doing that, and your MPGs will not be hurt.

I'd caution you, though, about setting this as a pattern. The driver behind you may not have been paying attention through the long read light and could see only a light turning green. If that driver forgets seeing your brake lights go off earlier, he may only see that your car has no brake lights on while there is a green light -- this could lead to a quick rear-ender as the driver behind you decides it is time to accelerate.

It also could lead to lower MPGs if you decide to hit the accelerator while you're in Park!

I put the car in Park at a RR crossing or if I need to access something in the back seat, on the floor, in the glove box . . . It has its safety value at times!

 

Here in Ireland if you rearend someone,you're at fault,if you come up behind a car that's actually stopped and doesn't have it's brake lights lit up and you assume it's moving,well IMO that's dangerous and bad driving,in any form of motoring always expect the unexpected,
As a lot of my driving is within Dublin city at night there's nothing more annoying than sitting in traffic with a car in front with it's brake lights constantly lit up,almost as annoying as those people who have no rear lights[and know it]and think using their rear fogs is a brilliant idea.
If i see someone coming up behind me when i'm stopped and who i think is travelling to fast i generally dab the brake pedal or put on the hazard lights as a lot of other motorists do.

 

Since the A/C in the Prius is electrical, it uses exactly the same amount of energy to run whether the car is moving or stopped. Yes, using the A/C will consume energy and therefore lower your fuel efficiency (unless you are on a long downhill, and re-capturing more energy by regenerative braking than the car can store in the battery). But this is the case whether you are moving or not. If you are in the fuel-economy competition and every fraction of an MPG makes a difference, then leave the A/C off. But if, like most of us, you have a car with A/C because you don't want to bake yourself inside your car, then run the A/C whether the car is moving or not. But just keep it at the highest temperature that you find comfortable. I usually find upper 70's comfortable if I'm wearing shorts and short sleeves, as I always am in hot weather. But then, here in Spokane we don't get much or severe hot weather.

With the car stopped, the engine will shut off. The battery will slowly discharge, and when needed, the engine will come back on and charge the battery for a while, burning some gas. But just because you're stuck in traffic and not moving does not mean that you should be less comfortable than when the car is moving. If you've made the decision to use a (really rather small!) amount of energy to keep the car comfortable, then run the A/C.

The Prius is designed so that you can use it exactly as you would use a conventional car. There's not much you can do to this car that will hurt it other than crash it into something.

 

This past weekend my wife and I ran the Avenue of the Giants Half-Marathon. We left our dog in the car for over 3 hours, which is something we could never have done with any other car than the Prius. I just left the car in Ready with the air conditioning turned on, left a window slightly open, and locked it up with the mechanical key. I also left a note on the windshield that the air conditioning was ON and the dog was OK. I really don't want anybody breaking a window to save the dog from his air conditioned comfort.

The gas mileage on the 300 mile trip to the event was at about 47.6. After the 3 hour idle with the air conditioning turned on, that went all the way down to 47.0. Was that a waste of gas? I certainly got value from it. If we had taken the BMW, it would have gotten something like 25 MPG, and there is no way I would have left it idling unattended for 3 hours.

Running the air conditioning in the Prius is so close to free that I just wouldn't worry about it. If you want to save more gas, don't take the trip.

Oh, and I frequently use Park at red lights. Once there is someone stopped behind me, I don't see any need for the brake lights being on. Actually, I feel more comfortable if a pedestrian crosses in front of me while I'm in Park than while I'm holding the brake in Drive. On stick shift cars, it is normal procedure to put the car in neutral at red lights - you're certainly not supposed to stay in gear with the clutch depressed for a long time.

 

Of course we'll say that. But it is completely unrelated to the issue of whether or not we are right. Did your mother teach you anything about men?

 

Another reason not to use park. If someone does rear-end you, you do NOT want your brakes set. If you see it coming, they recommend releasing your brake pedal if possible, which the impact may do anyway. If you set the parking brake, it won't release or dissipate the energy. No go on using the parking brake.

 

If I see someone trying to rear-end my Prius, I will shift into "R"....

 

I still worry that somebody will freak out when they see a dog locked inside a closed car in the heat. So in addition to leaving a note on the car, I also have a large thermometer visible from the outside to try to convince them that the air conditioning is really ON. Maybe a better note would be "Electric Air Conditioning ON - Dog is OK". The idea that the air conditioning could be running while the engine is not may be a difficult concept for some people. I'm not trying to convert them to driving a Prius... just trying to educate them enough that they don't break a window to "save" the dog.

Leaving a window cracked just a little would also allow them to check the temperature of the air by feel. But it would also be a security exposure. It wouldn't take much to put a coat hanger or such through the crack and unlock a door. Maybe a traditional steering wheel lock would be appropriate. What I'd really like is some sort of modification of the car to add a mode where the air conditioning runs, but you can't put it in gear. All that would take is an extra switch to disable the brake light signal (required to get out of Park).

Two other things I do to go low profile is that I turn off the video display, and block the speedometer display. Press the DISPLAY button, and then press "Screen Off". It comes back on when you press any of the buttons. The speedometer display can be blocked by placing a card flat on the dash, just in front of the speedometer. The image is projected up from the dash to the mirror where you actually see the image.

 

I know it's an old thread, but this makes me think 2 different hacks should be investigated:

1. A simple hack to activate the brake lights if the car is in park and on. (should be at most just a relay needed for this, and possibly just a diode)

2. A hack to allow the car to be on but not drivable as RobH mentioned. There are a number of ways to approach this, a proper one would likely be complicated.

Both of these could be implemented as a simple "dongle" that plugs into the DLC connector under the dash and sends/receives CAN messages to accomplish these things (and likely many other).

A cool product would be a low-profile dongle with DLC passthrough connector so you can still plug in things like scangauges, etc. It would also contain a USB port for connection to a computer that would enable you to program different options and update new features, etc. I'll put it on my list!