Friday, May 23, 2008

Gas prices solutions: 55mph speed limit vrs Telecomuting

So gas has hit $4 a gallon. Crude has hit all time highs and suddenly everyone is in a panic over what can be done. One proposal in particular is suggesting we go back to a national 55mph speed limit.

NO

It is not safer, and unless people actually adhere to the limit it will not do anything to improve gas mileage. It would improve ticket revenue however.

If you question my statement about safety just go look it up and find whatever sources you deem credible. There were more wrecks and more fatal wrecks by any measure made during the double nickel era and was followed by a sharp decline after it was repealed. Simple physics says it should be safer... less speed less damage etc. That is true enough but the problem is that the vast majority of people paid zero heed to the signs. Average highway speeds did not decline at the onset of 55mph limits... in fact average highway speed has generally increased over time with improved car design. Today's typical sedan is a far cry from a 70's piece of heavy iron with leaf springs. However because a fair percentage of drivers will ALWAYS adhere rigidly to the posted speed limits this meant there was often a greater relative speed difference between cars on the highway. Relative speed difference is what makes wrecks dangerous. It does not matter if we are talking about a car and a light post or two cars. The relative speed difference is the determining factor in how bad it will be. You also have to remember that the equation for deriving kinetic energy is exponential. That means the energy that has to be dissipated by a car moving at 80mph is not 4 times that of a car moving at 20mph... it is more like 16x the energy.

The equation is E = .5 (m * v^2) or Energy equals half of mass times velocity squared.

Use kg for weight and meters per second for velocity and you will arrive at joules. Map some speeds and you will see what happens. If everyone stayed within +- 5mph of 55 it would indeed be safer... but when speeds are split 55 - 85 that 30mph difference is worse than say a wreck between 25 and 55. Highway wrecks involving 55mph difference.. ie running into a stationary object.. are pretty much the same as hitting it at 85... you are just more sure of fatality to a few more decimal places. Crash tests generally take place around 35-45mph and very few cars can maintain their integrity at that speed much less higher velocity impacts.

So barring a completely different and vastly more effective enforcement mechanism there is no chance lowering the speed limit will increase safety or lower overall gas usage. Both simply because people will not obey it... not because the idea couldn't produce those results.

So what can be done about gas prices? Obviously numerous alternatives are in the wings. However for the most part those options are only in the wings because the higher price of gas has made them attractive. If gas went back down to $2-3 a gallon those ventures would dry up in pretty short order. Why? Because the new technologies are going to run consumers at least as much in total cost of owner ship as current cars with fuel costs around that level. Alternatives are needed so I am not that sure lower gas prices are a good thing. But if you want to lower them it is easy. You lower demand.

The majority of gas demand in the US is driven by the daily work commute of the average American. Cut a day of work and you cut that source of demand by ~20%. But I have to work you say? Fine... work from home. The overwhelming majority of white collar work in the US is computer based. We have this wonderful thing called the internet which virtually all said white collar workers have access to at home. They can do computer work at home and only come on days where face to face events are required. As a standing policy I would suggest a 3/2/2 workweek system. 3 in , 2 out and weekend.

Mon, Wed and Friday in the Office. Tuesday and Thursday as standard remote work days. That would produce a large drop in gas demand if it were implemented across the board in the US. It is realistic, and it is overdue. Lower traffic to work leads to lower gas consumption, less congestion, less smog, less emissions and improves quality of life as you spend less time away from home. It seems so simple. But decades of entrenched thought dictates what the work week is and means. While technically easy to implement this calls for a major change in how corporate bean counters and managers think.

2 comments:

Unknown said...

You can’t cheat physics. Any time you move an item you use energy, the faster you move an item the more energy you use. My father has a 2008 Chevy Uplander Van, at 65 MPH on flat land he is getting about 24 MPG, and 55 he is getting about 30 MPG. That is 6 MPG savings. So if we use a savings of 5 MPG times the vehicles in the Kansas City Metro and if there are a Million Vehicles then that would be 5,000,000 miles in savings for every 55 miles driven, or per hour. Now take this times the number of hours driven, times the number of vehicles driven in the US, you do the math. You speak of green houses gases, the more energy used, the more green house gases.

Tmortn said...

I did not suggest you could cheat physics. I said "...and unless people actually adhere to the limit it will not do anything to improve gas mileage."

Nothing wrong with your math. The problem is getting folks to actually drive at that limit in order to realize the mpg gains.