Leaburg Dam Vehicle Crossing Speeds with no Speed Bumps in Place

Transcription

1 Leaburg Dam Vehicle Crossing Speeds with no Speed Bumps in Place Saturday and Sunday, & 12 and Saturday, , with the speed bumps having been removed for the moment, I collected two sets of data. The first is of 109 vehicles when there were no pedestrians on the roadway. That's large enough to be of some statistical validity. The second is of 7 vehicles when there were pedestrians on the roadway. That's obviously not large enough to be statistically valid, but it does illustrate that pedestrian traffic is relatively infrequent. While I tried to be accurate, this is not intended to be a substitute for the data collection I am sure a traffic engineer would do, and I'm not a professional observer. Before considering the data, I recommend reading the link below: WITH NO PEDESTRIANS ON ROADWAY 85th percentile 15.4 mph Std Dev 3.3 mph date time vehicle type seconds mph direction :46 car roadway offset 8 feet :53 suv+trailer :54 pickup pier house 2 angle 60 degrees :55 pickup parallax correction feet :56 suv :58 car pier house 4 angle 15 degrees :00 car parallax correction feet :02 car :03 car net correction feet :05 pickup scaled distance 216 feet on Google Earth :40 car corrected distance feet :41 pickup convert to miles miles :42 pickup :43 car :47 car

2 :48 car :50 car :52 car :53 car :54 car :00 car :02 pickup :06 car :07 pickup :08 car :11 van :13 car :16 car :17 car :18 car :22 car :23 car :24 suv+trailer :26 car :27 pickup :29 car :32 car :33 suv :34 car :35 car :36 pickup :38 semi :39 car :41 car :43 suv :46 car :47 pickup :48 car :51 car For westbound traffic, timing started when the front of a vehicle started to disappear behind the east edge of pier house 4 and stopped when it started to disappear behind the east edge of pier house 2. Eastbound timing started when a vehicle front first appeared from behind pier house 2 and stopped when it first appeared from behind pier house 4. Timing by using the visual alignment from an angle of the front of a vehicle with the edge of a pier house creates a parallax problem because the vehicle is not in a true abeam position, so we need to correct for the offset of the roadway from the pier house edge. Using the roadway as one leg and a 90 line from the roadway to my position downstream from the Dam on the hatchery side as a right angle, then my lines of sight to the pier houses 2 and 4 east edges form two right triangles, and we can calculate the parallax correction necessary to account for the offset of roadway. The corrected distance is then used with the seconds to come up with the mph.

3 :55 pickup :56 pickup :57 car :00 pickup :01 motorocyle :02 pickup :05 pickup :06 car :07 pickup :37 pickup+trailer W :48 suv E :49 car W :51 suv W :57 car W :58 car W :59 pickup W :00 car W :01 car W :02 car W :03 pickup E :04 car E :07 van W :09 car W :11 car E :16 suv E :17 suv+trailer W :19 car E :20 suv E :21 pickup+trailer W :22 car E :23 car W :24 suv W :27 suv W :30 car E

4 :31 car W :32 car W :34 pickup W :38 pickup E :40 car E :41 car E :45 car E :47 suv W :48 car W :49 car W :50 car W :53 car W :54 pickup+trailer E :55 car W :56 van W :57 car W :58 van+trailer W :01 picup W :02 car W :03 car W :04 car W :05 suv W :06 pickup E :07 car W :08 pickup E :09 pickup W 85th percentile 10.9 mph Std Dev 3.8 mph date time vehicle type seconds mph direction :04 car :05 pickup

5 :19 car :38 car W :39 car E :40 car E :41 suv W During 2.8 hours of observations, pedestrians were on the Dam only 3 times even though all the observations were on sunny weekend days. One fisherman walked across, a man with two children walked onto the hatchery side a short ways, looked for a bit, and then returned, and a party of four crossed the Dam west to East. Relatively speaking, there is so little pedstrian traffic that getting a sufficient sample size to be valid will take a lot of time. One would expect, though, that the 85th percentile speed for when there are pedestrians would be less than that for no pedestrians. This is, in fact, what we see for the few observations we have. The 85th percentile speed dropped 5.5 mph.

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