i think they measure traffic volume

9/30/2005 3:14:33 PM

my roommate asked me what those were the other day- i thought everyone realized what they were, but apparently not

9/30/2005 3:27:39 PM

Quote :

"they dont measure speed or the placement (spacing) would have to be EXACT."

not really

9/30/2005 3:44:38 PM

someone once told me they were for measuring traffic volume

9/30/2005 4:20:30 PM

Quote :

"not really"

ok.. there are two ways they could measure speed.

1. they are going to measure speed by calculating the time it takes for each axle to cross the tube. this won't work b/c every wheelbase is different

2. the time it takes to go from one tube to the other. ok, so lets say it's calibrated for hte separation to be 4". if it is accidentally stretched, dislodged, or misplaced at a distance of 5", every speed would be recorded at 25% below actual.

9/30/2005 4:26:32 PM

[Edited on September 30, 2005 at 4:34 PM. Reason : misread your post, but yeah they are a lot farther than 4"]

9/30/2005 4:31:48 PM

they're generally much farter apart than that but...

they aren't securely fastened in place, most of the time duct tape holds them to the road

9/30/2005 4:32:01 PM

4" apart
45 mph = 792 inches per second

4"/792in/s = .00505 s
5"/792in/s = .0063131 s

4"/.0063131s= 633.6 inches per second (36mph)


12" apart
45mph = 792 in per second

12"/792in/s = .01515 s
13"/792in/s = .01641 s

12"/ .01641s = 731 inches per second (41.5 mph)

not that they do but they could get a good idea of the speed by putting two strips at least a ft apart

9/30/2005 5:06:27 PM

speed surveys are not done with the tubes

9/30/2005 6:22:15 PM

no shit

9/30/2005 6:29:55 PM

but i think they measure traffic volume

9/30/2005 6:35:10 PM

thats what i heard

9/30/2005 6:50:07 PM

i think they measure traffic volume

10/1/2005 10:10:46 AM

traffic is pretty damn loud too

10/1/2005 10:33:02 AM

Between myself, scottyc, and baonest

we've come to the conclusion

that the black tubes across the road

are used to measure traffic volume.

Now, continue your debate.

10/1/2005 5:33:04 PM

i'm just going by what a DOT man who puts the things out told me but what the fuck would he know? he said the single ones were for volume and the doubles were to get an idea of average speed on the road. i never said you could get a ticket from them.

10/1/2005 7:19:39 PM

they measure traffic volume

10/1/2005 7:21:32 PM