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mikeontraffic.com
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mikeontraffic.com is a personal blog at mikeontraffic.com. Since 2018, 8 different Hacker News readers have linked it 8 times, most often “85th Percentile Speed Explained (2016)”. No feed was found, so read it on the site itself.
Too few sampled comments (7) to say how often HN recommends it.?
Why HN links it
HN commenters link Mike on Traffic for traffic engineering explainers, such as the 85th percentile speed rule and per-lane vehicle capacity figures, often to back up points about speed limits and road design.
Summarised by Claude from a sample of 7 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- 85th Percentile Speed Explained (2016)3 people · 3 mentions · first linked 2018-09-19
- /numbers-every-traffic-engineer-should-know/2 people · 2 mentions · first linked 2024-03-27
- /numbers-every-traffic-engineer-should-know/2 people · 2 mentions · first linked 2018-02-28
What Hacker News says?
One way to assess these numbers is to conduct a quick sanity check. How many cars per minute or second would this be? 11.5 million cars/day is equivalent to : ~48,000 cars/hour ~8,000 cars/minute ~130 cars/second Clearly, somethings ... a tad off. 11.5 million cars per year however works out to: 31,000 cars/day 1,300 cars/hour 21 cars/minute Or roughly a 3 second headway per vehicle. Given four traffic lanes (two in…
Comment linking /numbers-every-traffic-engineer-should-know/
on “Baltimore's Key Bridge struck by cargo ship, collapses”Submitted 85th Percentile Speed Explained (2016) as a story · 2 points
HN discussionThis is actually a problem with speed limits that don't match the road or alternatively, roads that aren't designed to incentivize people driving the intended speed. In theory, the speed limit should be set to the 80th or 85th percentile speed of traffic, and the road should be engineered so that the 80th percentile speed is appropriate to the surroundings. https://www.mikeontraffic.com/85th-percentile-speed-explain…
Comment linking /85th-percentile-speed-explained/
on “Did your car witness a crime? Bay Area police may be coming for your Tesla”https://www.mikeontraffic.com/numbers-every-traffic-engineer... says one lane peaks around 1,900 vehicles per hour. Even if we assume each vehicle only carries one driver, we need 38 busses per hour (one every 95 seconds!) to match that capacity. In practice we're lucky to see two busses per hour scheduled.
Comment linking /numbers-every-traffic-engineer-should-know/
on “Traffic engineers build roads relying on outdated research, faulty data”Look up the "85th percentile rule". Traffic engineers actually generally aim to set the speed limit at the speed 85% of drivers are at or under. Sometimes politicians get in the way. For instance, it was requested to raise the speed limits above 55 mph in Chicagoland area highways, and the change was refused, even though the average driving speed on those roads is about 70 already anyways. Here's a good explanation:…
Comment linking /85th-percentile-speed-explained/
on “Self-Driving Cars Have a Problem: Safer Human-Driven Ones”According to [1], in California, total out of pocket for a first time cell phone violation is ~$150, total out of pocket for a subsequent offense is ~$250. Let's conservatively assume that for 75% of drivers, it's a first time violation. Average fine is $175. According to random internet search [2], the saturation flow of a lane of traffic is about 1900 vehicles per hour. Let's assume a 4 lane highway at rush hour i…
Comment linking /numbers-every-traffic-engineer-should-know/
on “Drunk-driver detectors for cars mandated in infrastructure bill”My understanding is that it is standard practice in traffic engineering to set speed limits to the 85th percentile speed of observed traffic. http://www.mikeontraffic.com/85th-percentile-speed-explained...
Comment linking /85th-percentile-speed-explained/
on “Electric Scooter Company Uses Technology to Go After Dangerous Riders”The numbers appear to be for how much traffic can pass in a single lane's worth of space. Their numbers make sense for a single traffic lane[1], one subway line[2] and one 2.5 meter (a bit narrower than a standard traffic lane) bike path[3], all of which take up pretty close to the same amount of space. [1] http://www.mikeontraffic.com/numbers-every-traffic-engineer-... [2] https://www.thoughtco.com/passenger-capaci…
Comment linking /numbers-every-traffic-engineer-should-know/
on “Automated Vehicles Can't Save Cities”
