Driving over a bridge- best technique?

<div class='quotetop'>QUOTE(larkinmj @ Jun 23 2006, 08:56 AM) [snapback]275819[/snapback]</div>

I too traverse a bridge in my commute, it is 1 mile long and is between a 65 MPH freeway and a 25 MPH city street. The speed on the bridge is posted at 50MPH, but almost everyone (until lately) does 60

In any case, I just lock cruise on 53 until the crest and then coast down to the interchange/street. Obviously, half is under power and the other is always coasting. I would not worry too much about MPG and more on safety and not being run over.

I think that to use heavier throttle to start and then feather is the preferred way.

As some have noted, a real short commute is not allowing the car to warm up to its most efficient operating temperature, so I doubt you will do any better. Is there a longer but flatter route that would allow the engine to 'come up' to temp and avoid the bridge? (In my case, there is one, but that would take me 20 more miles out my way (on top of a 47 mile one-way commute), so the little throttle on the bridge run-up is of little consequence.)

 

<div class='quotetop'>QUOTE(larkinmj @ Jun 23 2006, 11:56 AM) [snapback]275819[/snapback]</div>

I prefer not to use cruise control since it does not compensate for energy gained from the descent phase and lets it dissipate quickly. I tend to accelerate a little right before i crest and then as i crest - let go of the accelerator and then several seconds later accelerate and doing that way I get to dead band a lot. If you have a long descent your stored battery power will be used up b4 you get to the bottom of the descent. You can also gently accelerate down the descent and build significant reserve energy in the cars increasing momentum. I have several nice descents on my way to work and GENTLY accelerate all the way to about 74-75mph while keeping my mpg above 70! I use that energy as the road becomes flat and it carries me miles as i let the car slow down to around 55-57mph getting in the 90+mpg range!

Cruise control also locks you at a constant speed - there are times where you can slow down a little or maintain a slower speed going uphill thereby using less gas than if you were locked in at 55mph. That being said I tend to acclerate trying to keep the ICE going at around 70% of its max acceleration which I think is its max efficiency % - if you keep accelerating at to slow a speed you will not build momentum. When you accelerate like that uphill you find that you can ease off the gas pedal and feather it more as you get closer to the crest of the bridge.

Why dont you try different scenarios - reset your consumption screen to 0 as you get to the bridge and see what you get at the end of it using different techniques. I would be interested to see your results.

Using these techniques I am getting around 54-55mpg and this tank I am around 59mpg - I am 4 months into my Prius ownership and I have yet to "hyperinflate" my tires.

Have a nice weekend.

 

<div class='quotetop'>QUOTE(larkinmj @ Jun 23 2006, 10:13 PM) [snapback]276118[/snapback]</div>

I really can't add much more good advice except - Your mileage will increase substantially going over a bridge if you don't look down, close your eyes and "Let the Force be with You". Ed

 

<div class='quotetop'>QUOTE(larkinmj @ Jun 23 2006, 11:56 AM) [snapback]275819[/snapback]</div>

As long as you are not driving a Yugo, any mpg will be okay. We lost a Yugo off the Mackinac bridge a number of years ago; it just flipped off from a strong just of wind.

Tom

 

I have a number of bridges, although short.
I hit the accelerator in the pulse mindset and try to get a bit over the speed limit before the crest, then coast over the top & down the other side. Try it if you can......