SWMBO wanted to go for a walk last Sunday. It's early morning, little traffic so we went on my 5k route, it wanders into an industrial park and two streets that have little parking alongside them. Cause it's been icy one street that doesn't have a sidewalk is narrowed considerably compared to summertime conditions. So off we go and there isn't a single car through most of the walk until we are heading home along the narrow street that is ice and snow packed just off the pavement.?ÿ
We are over 2.5 miles into the walk and we approach a spot where there is a parked car on the north side of the street, we are walking along the south side, it is the only parked car along the entire walk. We are headed east and as we near the car a pickup shows up headed towards us from the west about 1/4 mile behind, then as it nears a car pulls into the street headed towards us from the east. We all meet at the same point, just as we cross the point were the parked car is, so it's us, both cars going east and west and the lone parked car along the 3 mile route. We finished the walk without seeing any other traffic.?ÿ
It got me thinking, do traffic engineers have a way to calculate the statics of random events like that; what would be the chances of the two moving cars meeting as they reach us walking since they were the only two cars we encountered in 5k, and then what would be the chance of meeting us at the lone parked car?
It seems to be impossible, no one would ever bet on it, but traffic does seem to move in improbable ways. ?ÿ
Like travelling down an almost empty interstate clustered with 5-10 other cars, no one behind or ahead for 1/2 a mile.?ÿ
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I am sure you have noticed how you could sit and watch a certain stretch of road for 20 minutes and observe no traffic whatsoever.?ÿ Pull out your survey gear and move to the middle of said road.?ÿ BAMMMMM. Traffic will instantly appear from all directions and continue throughout your need to be working in the road.?ÿ Return to your vehicle and observe a repeat of the earlier 20 minute absence of all traffic.
Like travelling down an almost empty interstate clustered with 5-10 other cars, no one behind or ahead for 1/2 a mile.?ÿ
I have no explanation for your experience while walking other than just bad luck.
The Interstate example can be explained by the tendency of a lot of drivers to get behind someone going what they consider about the right speed and just follow them. They don't want to put on the burst of speed necessary to pass in a reasonable time, if they only want to go the same or a couple mph faster.
Was there someone in the parked car selling little plastic bags full of something? That might increase the probability of a gathering by a fair amount.
One of the projects I worked on as a highway department surveyor back in the early '90s was collecting geodetic data for the State's bridge inventory.?ÿ We went by route collecting geo-locations on most of the 0ver 6000 highway bridges.?ÿ Now this was back in the day when we used critical mission planning software for static sessions as, at times, they might only be 3 or 4 SVs visible.?ÿ Painfully slow by today's standards, but really "Star Wars" kind of stuff back then.
On the existing bridge inventory registry that we worked from was comprehensive info on each structure; typical stuff like when it was built by whom, materials, load ratings.?ÿ It also had an ADT (average daily traffic) listed with the year it had been updated.?ÿ I was surprised to find out they actually put out counters and keep track of such stuff.
We all travel over the grand multi-span bridges on the interstates.?ÿ The unsung hero of public transportation bridge group is the rural single-lane, single span viaduct over the interstate or large creek.?ÿ There are thousands of these bridges that keep rural school buses, deputy sheriff's, hay trucks and the U.S. Mail toddling along the dusty back roads of the state.?ÿ Some of these bridges had ADT counts as low as 5 or 6 vehicles per day.?ÿ And the counts were only 2 or 3 years old.
But just wait until you get a receiver set up on a tripod straddling the bridge seat on one end or the other...every damned diesel or gasoline burning contraption in the township had to get across that bridge.?ÿ?ÿ Hay swathers with their headers attached were the worst.?ÿ With mere inches clearing the top of the parapet they would creep across the deck almost taunting us.?ÿ Then there the huge articulating tractors dragging ganged harrows and discs that were still wider than the bridge even when they were all folded up.?ÿ We always tried to find a spot for the receiver that was out of the clear roadway...but most of those bridges (and their approaches) were just too darned narrow.?ÿ ?ÿWe'd have to end the session, move the receiver, let the equipment pass, re-set up and start the session again.?ÿ Processing junk like that was painful sometimes.
Then I had the chance to chat with the folks in the Traffic Division about how they derived an ADT of 7 when I was out there for only 2 hours and counted 15 vehicles.?ÿ I was told they 'randomly sampled' periods of time during the day and then averaged them...So much for damned "statistics"... someone sat out there for an hour and saw 1 car so they probably figured the road had an ADT of 8.?ÿ Basically their numbers were wild-assed guesses and cartoons.
This was only one of several times I realized just how poorly a government bureaucracy spends tax-dollars to collect so-called "data".?ÿ
Yes, and since there were absolutely no cars in sight anywhere you didn't put out the required number of traffic cones.
Another experiment you could try is to draw a circle with yellow keil that is three feet greater in radius than your set up.
(That's three feet outside?ÿ your widest leg.)
No one will drive within it unless they drive through the whole setup.
When setup on the centerline why do people insist on driving around northbound in the southbound lane?
No one will drive within it unless they drive through the whole setup.
Dave, you've never surveyed in Fl. have you??ÿ ?????ÿ