Do we really need superhighways?

2022-06-13 0 By

| ao wen hu highway like video barrage, someone always think the speed is not fast enough.The rumor goes like this: the upcoming hangyong expressway reconstruction project in hangzhou will be a “superhighway” built according to the speed limit standard, with the speed limit increased to 150km/h.Although the specific limit, how much limit has not been officially confirmed, but it is so popular that many friends have been ready to punch the clock.The 120km/h legal limit has been around for years.Back then, when the Internet was budding, we opened our eyes to the world, and the Chinese network was once popular with the “German high-speed speed limit” (still quite new at that time) to urge the Chinese people to make progress and strive to achieve the double high of driving literacy and speed limit standard as soon as possible.2022 is a good year for high-speed travel.The new regulation, which will take effect on April 1, will eliminate penalty points for exceeding 20 percent of the speed limit, allow a speed limit of 120 kilometers per hour to 140 kilometers per hour, and add penalties for driving below the speed limit.Our high-speed safety regulations are moving from “pure no-speed” to “compliance and reasonableness”.This “150km/h superhighway” emerged at this time, naturally brought a broad space for imagination: our high-speed is not to speed up?150 km/h?According to known information, this rumor “according to the speed limit standard construction, speed limit up to 150km/h” highway, is for the Hangzhou Asian Games to prepare supporting projects.According to the description of “Hangyong Expressway Reconstruction Project in Hangzhou Urban Section”, the corresponding length is about 20 kilometers.Roughly from the eastern side of hangzhou city, southward across the Qiantang River, and then open to xiaoshan Airport near the whole line elevated.The project will be completed by the end of June as the Hangzhou Asian Games will be held in September this year.In the current public documents of the government, the design speed of the reconstructed section is still written 80-100km/h;However, the civil construction standard of the project refers to Germany’s unrestricted high speed (hence, it is called by some media as “Domestic unrestricted high speed”), making preparation for the future increase to 150km/h.In other words, the new highway has a hardware margin to exceed the 120km/h speed limit, but there is no specific time or extent to break the 120km/h speed limit.The rumor of “150km/h”, whether it is immediately implemented after the completion of the reconstruction project, or reserving the hardware for the future, there is no exact statement at present.Of course, “unproven” does not mean “denied”.Considering the background of the Asian Games and the value of the traffic trunk line, if in a special period of time, under the escort of some measures, as a high-speed speed increase test pilot section, it is not out of touch with reality.120km/h, really not slow most of you should be aware that the maximum speed on the vehicle parameters sheet does not represent the speed you can actually drive.It is possible that the time required to accelerate to maximum speed is too long to encounter such a long open road in reality;It is also possible that the vehicle’s condition may drop too far near top speed to give the average driver sufficient confidence (as in “drifting”).But today, the car itself is no problem at the speed limit.The comprehensive quality of contemporary family car can easily cope with the high-speed cruise above 120km/h.Top speeds are generally more than 180km/h, even for vehicles considered weak.Even if some allowance is left below this speed, there is at least a few dozen km/h of room for improvement above the current 120km/h limit.The reality, however, is that the speed limit in most countries around the world remains at 110-130km/h and has not increased significantly for decades.Germany has unique unrestricted motorways, where about a quarter of the roads are speed restricted, and the limit is just 130km/h: there is no higher limit on the speed required because the rest of the road is unrestricted.Germany’s “unrestricted” speed limit part, the maximum speed limit is 130km/h110-130km/h, can be said to be the absolute mainstream of the global highway speed limit.In this range, there is no need to be exhaustive. The “speed increase” we are discussing today is at least 150km/h, compared to 120km/h or 130km/h, there is no essential difference.In Korea, the legal speed limit is 120km/h, but many highways are 110km/h or 100km/h due to old and narrow roads.The limit below 130km/h can be classified as one category, and there is only one exception in the world, Germany.The autobahn is a product of historical accumulation and cultural environment that no other country can match.It’s not an “us versus them” gap, it’s a “world versus them” gap.The first time I drove on a German autobahn, what struck me most was not the speed limit, but the rules of driving: turning signals in advance when changing lanes, returning to the lane when overtaking, never (and never) passing on the right.Too many people have talked about this, and I want to say that even allowing for differences in overall driver ability and quality, we don’t need to compare Autobahn anytime soon.Compared with the global village, our 120km/h is not top, but it is not slow in any way.So does this “world standard” need to be raised?How many minutes is a hundred kilometers worth?China’s 120km/h first appeared in the 1980s and has remained unchanged for 40 years.70mph (112km/h) in the UK was the norm in 1967, so much so that the early TopGear trio’s jokes about British motorways became routine.The speed limit in many countries has not been increased for many years.There has been a lot of discussion about how much the speed limit should be, most of it referring to road design standards and vehicle safety.But that doesn’t explain why the speed limit has not changed over the decades as technology has improved and cars have become safer.It doesn’t explain why if you want to be safe, why don’t you just lower the speed limit even more?Why is 110-130km/h the consensus of all countries?We might as well assume that the hangzhou-Ningbo expressway in the urban section of Hangzhou is really raised to the 150km/h speed limit, what changes will be brought about?At the current speed limit, it takes “20km÷120km/h×60min” =10 minutes for a car to pass this section of 20km high speed, assuming the whole 120km/h cruise without any acceleration and deceleration.When the speed limit is increased to 150km/h and the whole speed is 150km/h, the 20km journey needs “20km÷150km/h×60min” =8 minutes.10-8 = 2 minutes.Going from 120km/h to 150km/h, a 25 percent increase, or 30km/h, can save you two minutes, you read that right, 120 seconds.What if we make it longer?I found a data in 2017. In that year, the average number of high-speed trips was 16 and the total distance was 1129km, that is, the average distance of each high-speed trip was 70km.Let’s be more generous with 100km, or should we assume that the ideal condition is the whole journey without acceleration and deceleration, the speed limit of 120km/h will take 50 minutes, and increase to 150km/h?40 minutes, 10 minutes saved.Again, this is ideal, but it’s going to be less, not more.The time savings will certainly increase as we travel further, but remember that as we continue to travel beyond 100km, our chances of taking to the road plummet.When was the last time you exceeded 100km one way on high speed?How many times a year?How much would you pay for a hundred miles to save a few minutes?The 150km distance between Shanghai and Hangzhou, the ultimate ideal state is 15 minutes earlier to balance the benefits and costs. Is this the end?Isn’t.If it costs nothing to save 10 minutes /100km, it’s worth it anyway.How much would it cost to save 10 minutes per 100km on average?Let’s put aside the problems that can be solved with money and focus on security first and foremost.To assess the level of risk, we take momentum as a very crude basis.Given the low probability of hitting a stationary object on a highway, lower the bar a bit and take the difference between the kinetic energy of the maximum speed limit and the kinetic energy of the two thirds speed limit.A 25% increase in speed from 120km/h to 150km/h saves 20% of your time, and how much does the difference in kinetic energy of a slow car 2/3 of the speed limit increase?- 56%.The kinetic energy difference between the speed of 150km/h and the speed of 100km/h is 1.56 times of that between the speed of 120km/h and that of 80km/h.Even if we chose the 40km/h difference (120-80) instead of “2/3”, that is, the kinetic energy difference of 150km/h relative to 110km/h, this number is 1.3 times larger.Speed is increased by 25%, time is saved by 20%, and risk is increased by 30% to 56% (depending on whether the speed of slow cars is proportional or differential).The above definition of “risk” is extremely crude and limited, but you can understand what I’m trying to say: increasing the speed limit is not a good deal.Not to mention, greater kinetic energy relative to slower cars is just one of many safety risks, and safety is just one of many problems associated with superspeed (flat tires, too many).Not to mention, saving 20% of the time is not low, but it is most closely related to the speed limit of passenger transportation. The high-speed mileage that people can bear is limited, and the efficiency improvement of 10 minutes in the ideal road condition is only 100 kilometers, which has little impact on people’s life pace.Not to mention, the time-saving effect is based on the assumption that the speed of the cruise will be smooth and uniform, and the benefits of increasing the speed limit will be discounted in reality.Add up what we’ve talked about and what we haven’t talked about, and who has the incentive to increase the speed limit?Or is it really cost-effective to increase speed limits on a current basis?120km/h to 150km/h, it seems to be angry to raise 30km/h, a full 25%, a fierce operation like a tiger;On closer inspection, the impossibly perfect road conditions save only 10 minutes per 100km, and that’s not even taking into account all the increased costs and risks.In a word: speeding up too aggressively is out of your mind.Why stopped at 120km/h?So that’s it, let’s review the elementary school formula, t=s/v, time = distance/speed.Under the premise of the same distance, time and speed are inversely proportional, which determines that the speed of each increase in the same range, can save less and less time!It’s called diminishing marginal utility.1km distance, from 100km/h to 200km/h, time reduced from 36 seconds to 18 seconds;From 200km/h to 300km/h, it only goes from 18 seconds to 12 seconds.According to this principle, if the speed limit is reduced by 30km/h from 120km/h to 90km/h, the journey time of 100km will be 67 minutes, an increase of 17 minutes (+34%).By contrast, a 120km/h upgrade to 150km/h saves only 10 minutes (-20%).The higher the speed increases, the less benefit it will bring.So the world ended up with a mainstream speed limit of 110-130km/h, so even though the performance of cars has improved dramatically over the past few decades, there has been no incentive to increase speed limits.This is a perfect balance: if the speed limit is lower, there is a considerable incentive to be efficient, and the speed limit tends to return to the balance as long as the technology supports it.If the speed limit continues to be raised, the benefits will have little impact on people’s lives and the increased risks and costs will not be appreciated.So the speed limit will stay at 110-130km/h until the world ends?Of course not.The description of hangzhou-Ningbo Expressway actually gives the answer, “through intelligent systems, vehicle control and other means”, to increase the average speed of about 20%-30%.The diminishing returns of increasing speed will not change.But if it costs significantly less to speed up, there is a stronger incentive to achieve extreme efficiency;If people accept longer high-speed journeys, the time saved can add up to more.The current 120km/h limit is justified because it is now balanced.But in the future, intelligent driving, V2X and other technologies will reduce the risk of high-speed driving, and the concept of long-duration high-speed travel (such as autonomous driving at night) brought by driverless technology will likely upset this balance.The hangzhou-Ningbo expressway upgrade project also mentioned that science fiction technology such as wireless road charging will be added in the future.Considering that the efficiency and cost of road surface wireless charging are still far from practical, this is obviously a layout planning in advance for the long-term future, as a verification and pilot of future technology.So stop thinking it’s for you and me, it’s for the whole future of road transportation.Does it still matter whether the speed limit will be 150km/h after completion?The pattern could be opened up a little bit more.Simply raising the speed limit to 150km/h, large passengers continue to run 100km/h, large goods continue to run 80km/h, what is the meaning of the world?The exploration goal of this road should be the all-round speed increase of the overall highway traffic system.Infrastructure maniacs are no longer a thing. Now we need to be pioneers in no man’s land.