The 85 percentile
In the picture above: 5 seconds earlier the guy tailgating the camper couldn't see the bicycle. Of the three vehicles (car/ Camper/ Bike) in the photo: the State police speed test was set up only to count the tailgater (is that a fair representation of Lakeshore Traffic?)
Could Tens of thousands of bike trips per year on Lakeshore each temporally hidden from view by large vehicles, be considered a hidden hazard? YES
Could Tens of thousands of bike trips per year on Lakeshore each temporally hidden from view by large vehicles, be considered a hidden hazard? YES
the State police, the county road commission & the township
WHO SETS SPEED LIMITS?
State law assigns the responsibility for setting speed limits on county roads (those under the jurisdiction of the county road commission) to the Michigan State Police in conjunction with the local road commission. In the case of county roads in townships, the State Police, the road commission and the township board must unanimously agree on the speed limit. If it desires, the township board may opt out of the process.
State law assigns the responsibility for setting speed limits on county roads (those under the jurisdiction of the county road commission) to the Michigan State Police in conjunction with the local road commission. In the case of county roads in townships, the State Police, the road commission and the township board must unanimously agree on the speed limit. If it desires, the township board may opt out of the process.
Why have past attempts to lower the speed limit failed?
Each governing entity has different concerns and unanimous agreement is needed.
1) The Michigan State Police: Cares about 85 Percentile, variation of speed, and hidden hazards.
2) The Road Commission: Cares about: The Nature of the road, and making the road accessible to all users.
3) The Township: cares about all road related issues, including noise and quality of life.
To be successful we have to convince each entity that lowering the speed limit fits their goals with their formulas.
Each governing entity has different concerns and unanimous agreement is needed.
1) The Michigan State Police: Cares about 85 Percentile, variation of speed, and hidden hazards.
2) The Road Commission: Cares about: The Nature of the road, and making the road accessible to all users.
3) The Township: cares about all road related issues, including noise and quality of life.
To be successful we have to convince each entity that lowering the speed limit fits their goals with their formulas.
Although local government may consider quality of live issues; like road noise, pedestrian safety and comfort, or home values: the state police will not. They use the 85 percentile formula -only, and they hold veto power over the other two branches of government. The last test for Lakeshore Drive was (date 9/10/2015 @ 9:50- 10:30 am) location was on Lakeshore south of Ferris, (54 MPH was the 85percentile result) So they want to keep it at 55MPH. See sampling problem.
Regarding the photo below...These people and the many like them get their mail with their backs turned to 55 MPH traffic- while road construction crews are protected with a 45 MPH speed limit. |
Sampling Problem?Representative sampling: Institute of Traffic Engineers: "the more uniform the speed of vehicles in a traffic stream the less chance for conflict and crashes." Lakeshore drive has an very high level of trailer traffic (campers and boats) as well as the highest number of bicyclist on any road in the county. 1) The last State police test (date 9/10/2015 @ 9:50- 10:30 am) Lakeshore south of Ferris, most of the camper trailer and nearly all of the boat trailer traffic is south of the test site- After Camping season. At a time of the day without Bicycles. You couldn't design a test better if your goal was to exclude all slow moving traffic. 2) If Bikes, have the same rights & responsibilities as cars. And subject to the same speed limits- then why don’t I see bikes reflected in the traffic numbers? ( total count, or speed). So, you have a test that avoids nearly all the slow moving traffic! If the test is not representative on the vehicles driving on lakeshore than how can the formula be representative of the real 85 percentile's speed? Lakeshore drive currently has a Prima Facie Speed Limit of 55 MPH south of Brucker, and 45MPH to the north to Serenity How the number of Access points-driveways-effects Prima Facie calculations: " 25 miles per hour on a road with 60 or more vehicle access points (side streets, driveways, private roads, etc.) within a half mile. " 35 miles per hour on a road with 45 to 59 vehicular access points within a half mile. " 45 miles per hour on a road with 30 to 44 vehicular access points within a half mile. " 55 miles per hour for all other roads with no posted speed limit. This is known as the "general speed limit.” *so, this mail box generates 18X more pedestrian traffic, and cul-de-sac generates 18X more turn in/out traffic- Yet, the Michigan State Police consider it one (1) driveway - does that reflect reality in any way? Adjustments are warranted in the 85 percentile rules. A -7 MPH adjustment can be made for hidden hazards (drives etc.) |
State Police use the 85
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DETERMINING "REASONABLE AND PROPER" SPEED
Road agencies around the country have established standardized methods for determining reasonable and proper speeds. These include engineering and traffic studies that examine such things as traffic volume, accident rates, the character of the road (whether there are sidewalks, the number of driveways, sight obstructions, etc.), pedestrian activities and potential hazards that might not easily be detected by drivers. * THE 85TH PERCENTILE The 85TH percentile speed is the speed at or below which 85 percent of traffic is moving, based on radar checks. Studies indicate posting speed limits higher or lower than that driven by 85 percent of drivers does not significantly change the speed of those drivers. The 85TH percentile rule recognizes that the other 15 percent of drivers often drive above a reasonable speed, given the conditions. The studies suggest this 15 percent of drivers causes a disproportionate amount of the accidents and has the worst driving records. Additionally, the Michigan State Police generally will not sign off on a speed limit that is not reflective of the 85TH percentile. When the Michigan State Police block a speed limit change They're simply saying they can't enforce a slower speed limit, on the road, as it currently is designed. -The County Road Commission NEEDS to build/Design a slower road. See the video on traffic calming. on the home page. |
is there any adjustments to the 85 Percentile rule? YES! |
How we get to 45 MPH: Using MDOT rules. (for our short term goal)
Modified Speed limit: Police:85 percentile : formula adjustment -7 MPH for hidden hazards: MDOT regulation guidelines, page 6 (see attached) “If there are hidden hazards of any exceptional nature, then a modified speed limit may be set within five to seven mph of the 85th percentile speed. “ Page 5, 2nd,3rd, 4th paragraphs : MDOT regulation Guidelines. (highlighted, in the MDOT guidelines -see read box above) Lakeshore has many hidden hazards: Hidden Driveways, Bikes hidden by other vehicles, campers hidden in plan view, going 20MPH less than expected. Hidden and distracting views of the lake. The last State police test (date 9/10/2015 @ 9:50- 10:30 am) Lakeshore south of Ferris, (54 MPH) 54 MPH -7 MPH adjustment for hidden hazards = 47 MPH round to 45MPH : MDOT regulation guidelines page 6 “Speed limit recommendations between adjacent sections of highway outside incorporated cities/villages should generally be made in increments of 10 mph. “ |
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