Originally posted by: Evadman
Originally posted by: TallBill
True. I'll pull out my book when I get home and see exactly what the statistic is.
It needs to be based on crashes per mile, or deaths per mile traveled or something close. Otherwise, the numbers will be skewed because there was way less travel during WW2.
Ok, pulled out my book "Understanding Police Traffic RADAR & LIDAR", it's a manual for teaching police radar/lidar, I'm actually a certified instructor.
Data is definitely not that amazing for WW2:
The national war speed limit of 35 mph was implemented in the fall of 1942 to conserve fuel and tires.
Format is Year, Fatalities, Million Vehicle miles
1941 - 38,142 - 333,612
1942 - 27,007 - 268,224
1943 - 22,727 - 208,192
1944 - 23,165 - 212,713
So the deaths per million miles before ('41-'42) was .108 and the deaths per million miles in ('43 - '44) were .109. Statistically the sample is obviously way to small but the rate is almost constant before and after the change. Perhaps people just traveled less because they didn't want to go slow. If you count that as saving lives, I guess it worked. I wouldn't though.
The book also has data for Vietnam when an oil shortage led to a national speed limit of 55 mph near the end of 1973
Format is Year, Fatalities, Billion Vehicle miles
1971 - 52,542 - 1,179
1972 - 54,589 - 1,260
1973 - 54,052 - 1,313
1974 - 45,196 - 1,281
1975 - 44,525 - 1,328
Deaths per million miles before the limit ('71-'73) was .043. Deaths per million miles in ('74 - '75) was .034. So there was a huge drop when speeds lowered from 60+ to 55, but once again we are from from statistical proof.
One interesting note is the overall huge drop 3 decades later in fatalities per miles traveled. Almost 60% less per mile traveled.
The real problem from increased speeds are obviously total stopping distance and kinetic energy. Using numbers from my book I'll post the total stopping distance of a car which includes recognition time of .9 seconds, reaction time of .75 seconds, and actual braking distance. I'll also post the kinetic energy that a 3,000 lb car has at the same speeds (as if it did not stop at all or was still slowing).
Format is Speed, total stopping distance(feet), Kinetic Energy (in foot pounds).
25 - 91 - 62,914
35 - 144 - 123,312
45 - 207 - 203,843
55 - 280 - 304,506
65 - 362 - 425,301
75 - 454 - 566,231
85 - 556 - 727,285
Draw whatever conclusions you want from this, but it does lead to yet another chart. This one has a scenario where there is a sudden obstruction to your lane that occurs 210 feet ahead of your car.
The format is your car's initial speed, reaction distance, braking distance, and speed at impact, since reaction and + braking distance can only equal 210. Coefficient of braking is .70 (dry roads)
55 - 60.5 - 147.0 - 0
60 - 66.0 - 144.0 - 24
65 - 71.5 - 138.5 - 36
70 - 77.0 - 133.0 - 46
75 - 82.5 - 127.5 - 54
This one is pretty obvious. 210 feet is probably even large for a following distance on a highway. Even 5mph difference makes a huge difference, especially when you look at the kinetic energy table.
Phew, this manual has a lot of info in it, the rest is mostly about the actual operation of equipment and procedures. At least worth looking at.