Truck Air pollution????

[uphillklimber]

x

 

[David Metsky]

Well, duh, if I'm going 3 miles per hour faster, I'm making more pollution, but for a shorter period of time.

Actually, it doesn't work like that. You'll be getting worse gas mileage at higher speed due to wind resistance. Unless you are coasting, your engine is turning the same number of revolutions to get you the same distance, and you'll burn more gas. If you are measuring in gasoline burned, slower (to a point) is better.

I have no opinion on the rest of the message, but just wanted to point out a logic flaw.

-dave-

 

[MichaelJ]

I was always under the impression that truck regulations on highways (such as the requirement in Massachusetts that on all highways of 3 lanes or more trucks are allowed only in the rightmost two) are to minimize speed changes on uphill grades. Traffic flows much better when everyone isn't suddenly forced to slow down or make rapid lane changes because a loaded truck is trying to get up a 4% grade.

 

[David Metsky]

Isn't there an optimal cruising speed, at a certain point, don't you get your best gas mileage at "X" mph? Depending on how the trucks are geared, and cars, for that matter. Hasn't Detroit geared vehicles to get their best gas mileage at the national spped limits?

To a point, yes, but the optimum speed is probably something around 45 or 50. Air resistance goes up as a the square of speed, no matter how efficient the gearing is, after a while you are getting worse mileage.

One cite: http://www.cartalk.com/content/eco/tips.html#6

Because wind resistance increases dramatically with speed, for every mile per hour over 55 that you drive, your fuel economy goes down by 2 percent. In other words, you'll get about half the mileage driving at 70 mph compared to 50 mph!

 

[riverc0il]

in my drivers ed class many many years ago, i was told that 55 is the optimal speed limit on the highway in consideration to both time and gas efficiency. anything less you're not saving enough gas to justify the loss of time, whereas higher than 55 begins to impact gas usage faster.

i generally drive at 70mph on highway trips to the whites. i find that when i increase my average speed to 75, i use on average 25% more gas to save less than a half hour of time, not worth it imo.

 

[MichaelJ]

Anybody got a car with a real-time MPG display? I know numerous models do, if you splurge for the onboard computer extras. That would be pretty interesting ... a practical experiment.

 

[Uno]

...

I used to have a digital milage meter in my old Buick but I found it didn't work correctly. It was in a car from the late 80's so maybe it was too old tech. When I compared my actual milage to the milage on the dash the dash always showed me getting better milage than my actual.

I used to drive a truck (moved mobile homes from the Midwest to the Northeast mostly). It never bothered me (Ohio had a similar rule about that last lane). The reason it was nice to have it there was to keep the cars moving around us.

There were drivers who drove us nuts however! Like the people who set their cruise, sit in the middle lane and never move over regardless of the trafic around them. It forces those who are going faster in a truck to either pass illegaly on the left or the right. I swear some of these people thought it was their duty to slow everyone on the highway down! lol

On a seperate topic. Please don't rush to pass a truck then abruptly stop to turn left a short distance farther down the road. It really is annoying and happens much more than you would think.

 

[skican]

Some people do think it's their job to slow people down. My favorite, the brake dance when they think you are approaching too fast. I always wonder if whip lash for life is worth the old brake dance slow down. I hate driving these days. Too many freaks on the road.

 

[sledhaulingmedic]

I drove for a contract bakery when I was in college. (I "hauled buns" 8) ). Many, many round trips Boston to NYC. My impression has always been that the lane restrictions were to keep car traffic flowing around slower truck traffic.

In some ways, these restrictions are out dated. In the days when tractor trailers might have engines good for 300HP and 1000ft/lbs of torque to pull 80,000 lbs, it made sense. Now, 400 to 500HP and up to 1800Ft/lbs, it makes more sense to allow trucks to use the 3rd and 4rth lane, as long as they don't dwell there and clog things up. Personally, I say remove the restrictions, but strictly enforce the concept of "Keep right, except to pass" for ALL vehicles.

I have heard that in some areas, the restricted left lanes are not built with as much base material, and would not holdup to heavy truck traffic. I think this is an urban legend

 

[smitty77]

I have heard that in some areas, the restricted left lanes are not built with as much base material, and would not holdup to heavy truck traffic. I think this is an urban legend

Actually this is the God's honest truth. The majority of all fatigue wear in a pavement comes from trucks, and therefore more attention is paid to the truck lanes when a road is constructed or slated for rehab.

For a rehab/reconstruction, past traffic data (along with years of weather data) for the highway in question is reviewed and the type and thickness of pavement is selected so that it will serve X years after which some form of maintenance work will be required. The kicker is engineers will sometimes specify a thinner or less "robust" pavement for the outside lane as there will be no appreciable truck traffic in that lane. The same holds true for breakdown lanes and shoulders.

When traffic counts for a section of highway are done, the far lane isn't even monitored because the loading effect of cars and light trucks is less than 10% of the effect of a big truck.