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Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Y <blockedofcourse@foo.invalid> Newsgroups: sci.electronics.design Subject: Re: Speed limiters Date: Sun, 7 Jul 2024 13:44:59 -0700 Organization: A noiseless patient Spider Lines: 262 Message-ID: <v6euod$g0q4$2@dont-email.me> References: <v69vj4$3fu0d$1@dont-email.me> <v6bd03$3qa8v$1@dont-email.me> <v6cedi$3v8g0$3@dont-email.me> <v6dlku$8e0f$2@dont-email.me> <v6dooj$9h9s$1@dont-email.me> <v6ekjd$e0lt$1@dont-email.me> <v6ep5q$ej56$2@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sun, 07 Jul 2024 22:45:02 +0200 (CEST) Injection-Info: dont-email.me; posting-host="f9971c8e980327526a20b7a4d42fe357"; logging-data="525124"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1920HyhYmprQSGIaQjuCxsA" User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Cancel-Lock: sha1:FOAM/yGcaFLA90GRreXZLeVgNZA= In-Reply-To: <v6ep5q$ej56$2@dont-email.me> Content-Language: en-US Bytes: 14078 On 7/7/2024 12:09 PM, Martin Brown wrote: > On 07/07/2024 18:51, Don Y wrote: >> On 7/7/2024 2:56 AM, Martin Brown wrote: >>> Investment in "smart motorways" which allows them to use all 4 lanes as live >>> running lanes (3 properly designed to be running lanes and one hard shoulder >>> intended as a refuge for broken down vehicles). >> >> How does "smart" make that possible but "not-smart" doesn't? >> Do your roadways "change directions" based on time of day? >> (we have center lanes that do so to expedite traffic into >> or out of busy areas based on traffic patterns -- but, they >> are time driven) > > In theory the smart motorways are monitored along their length by cameras and > control rooms. Each lane has a tick or a red cross above it to indicate if it > is in use or not available. At peak times all lanes are run live which leaves > no room for error whatsoever. I don't understand -- they are taking capacity OUT of service? > Emergency vehicles have to fight their way through traffic if something happens > (as opposed to going down the non-running lane hard shoulder). That seems to be a bigger problem "in town", here. Largely because traffic is naturally stopped at frequent intervals along any travel route. Convincing three lanes of "parked" (at traffic signal) traffic to get the hell out of the way for an emergency vehicle approaching from behind is a bit of a chore. Such vehicles are equipped with a strobe light that visually signals a sensor mounted high in the intersection. It ties in to the local signal controls and overrides the timing to allow traffic along the "approach axis" to move, even if it would normally be halted. In theory, that traffic starts moving (making the blockage more fluid) and they can then get out of the way of the approaching (from front or rear) emergency vehicle. Too often, drivers "freeze" thinking that the emergency vehicle can sort out its dilemma. For undivided roadways, the emergency vehicle will often cross the centerline to use the lanes in the opposite direction to get around idiot drivers "ahead" of it. >> [IIRC, DC? had similar roads that would change direction >> based on time of day] > > There were a few of those in the UK. One in Manchester London Road 4 lanes > under flow control depending on the time of day. 3 in for morning rush hour and > 3 out in the evening they were notorious for head on crashes. Picture from the > late 1970's: > > https://www.flickr.com/photos/gmts/33623521145 > > An even worse configuration in the 1970's was the three lane trunk road with > the centre lane for "overtaking only". They resulted in the most spectacular > head on crashes (think 150+mph closing speeds) and caused collateral damage in > the adjacent lanes. Not survivable. The center "suicide" lane in most roads, here, is for taking left turns across traffic (remember, we drive on the right). It also finds use for traffic trying to enter the roadway via a left turn; they can pull into the middle lane and essentially *sit* there until it is clear to pull further to the right in the right lanes. >> Most roads have predefined lanes in each direction. Some roadways >> are further (physically) "divided" to isolate traffic from each >> direction. > > UK motorways have strict central reservation barriers which are being > reinforced to heavy weight solid cast concrete with tensile steel inside to > stop the larger HGVs going straight through them. Our "interstate" highways tend to have a large median between divided lanes. So, crossing over the "center line" ends up with a vehicle in grass/ditch. Of course, this is only possible in places with ample real estate. Such roads traveling through metropolitan areas can be hazardous as the concrete "prisms" placed end to end are really only massive enough to *deflect* traffic, not *stop* it. This is particularly true of East Coast cities where "walking trails" became early roadways... <https://en.wikipedia.org/wiki/Cross_Bronx_Expressway> <https://en.wikipedia.org/wiki/Interstate_495_(New_York)> <https://c8.alamy.com/comp/BR80PR/traffic-on-storrow-drive-in-boston-massachusetts-BR80PR.jpg> Though there were roadways in Chicago that were similarly harrowing: <https://upload.wikimedia.org/wikipedia/commons/b/b5/The_Loop%2C_Chicago%2C_Illinois%2C_Estados_Unidos%2C_2012-10-20%2C_DD_03.jpg> Your car seems DRAWN to those metal uprights IN the roadway! (I have no idea how they managed to film The Blues Brothers car chase -- and subsequent police car pileup -- there!) Likewise for Lower Wacker: <https://i.pinimg.com/originals/d1/dc/44/d1dc443826f2c9fde43456351a4c7f8d.jpg> <https://c8.alamy.com/comp/WDK97R/intersection-on-lower-wacker-in-downtown-chicago-WDK97R.jpg> >>> It didn't take account of dumb drivers or of the need to properly maintain >>> the camera systems used to monitor the road situation. As a result they are >>> having to add a lot of extra refuges to the "smart" motorways to make them >>> safer after several very high profile nasty high speed collisions between >>> motorway traffic and broken down vehicles. >> >> Stopping *on* the roadway is often forbidden. Your vehicle must be >> pulled off, onto a shoulder (outside the outside lane -- far right in >> our case). > > That is the point of "smart" motorways. There is no hard shoulder to pull off > onto - it is a live lane just like all the others. You can't always control > where you breakdown either. There are refuges from time to time but far too far > apart to be any use. Ah. Most roads, here, have a shoulder -- though sometimes "soft". It is not uncommon to see someone trying to change a flat tire on the driver's side ("in-side" of the roadway) of their vehicle. A patrolman will "run interference" for you *if* he comes upon you. Otherwise, you work with one eye always watching oncoming traffic. Police officers are often at risk in roadside stops as the *vehicle* may be on the shoulder but the officer standing beside the driver's door/window will have his ass out in traffic. ["distracted drivers" care little about what they may hit!] > In my student days we got stuck immediately behind a vehicle in the outside > lane (long before mobile phones). What happened next was very interesting. A > pair of heavies saw what had happened from a distance behind us and created a > rolling road block. When they had stopped all the traffic we got out and pushed > the dead car onto the hard shoulder and then got back in our car and continued > our journey. It was touch and go whether someone would pile into us when we had > to stop like that. > >> A patrolman encountering such a vehicle will likely park his vehicle >> upstream of it to further alert oncoming traffic to the hazard. > > Same in the UK. Highways agency vehicles have damn big flashing please don't > hit me signs with an arrow that can be erected behind them. Police will usually walk back upstream and deploy flares to warn of their stationary presence, "ahead". >> Work on the roadways (overhead signage, pavement, etc.) usually results in >> overly long stretches being cordoned off ("dunce cones") to ensure traffic >> is clear of the work area BEFORE encountering it. > > There is a lot more of that work at the moment because of the crisis with > smart/dumb motorways. They are dumb as hell when the smarts that are supposed > to keep them safe are not working! "Something" is always under construction, here. You may travel across town and stumble onto three or four different "projects" if you are unlucky enough. It isn't practical to try to keep track of all of them (though the news media cover them nightly along with appraisals of current travel times) unless your normal travel route has you encountering them. The standing joke is that they will pave a roadway (we recently were asked to approve $1B -- 10^9 -- for road repairs "in town") and, as soon as the asphalt has cooled, they will dig it up to work on the SEWERS below! (something about left hand not knowing the right hand even EXISTS!) For a while, firms wanting to install communications infrastructure were essentially given a free pass to work anywhere they "had to". And, of course, company A and company B rarely share their plans with each other... >> And, most roadways enter and exit on the outside (right) lane so you >> can predict where the "varying" traffic will originate. > > Opposite sense in the UK, but we do have a few free for all junctions on urban > motorways where traffic is injected and must leave from the outside (fastest) > lane. A recipe for high speed collisions. "Rotaries", here. No traffic control signals as they are intended to keep traffic MOVING. Not a place for the timid! ========== REMAINDER OF ARTICLE TRUNCATED ==========