Frequency of Changing Lanes

Something to observe – in Shanghai, the frequency of changing lanes on the road is very high, if not a constant action. People will shift from one lane to another, and to another, and back and forth, all the time.

The frequency of the same action is so low in the bay area. Generally people need to change lane just few times in the whole journey. For example, get onto the University Ave, follow the one lane street, and choose the lane going to US-101 later. Keep the lane on the right before getting the ramp exit, and then follow the lane to hotel. That was a typical route.

Drivers’ behavior difference is obviously the reason, maybe the only direct reason, but there must be deeper reason for the difference. What are those reasons?

Speed Difference

Speed difference of cars. Look at the cars on road of Shanghai. They drive in completely different speed. Some drive at 60 km/h, nearby cars are running at 80km/h, while others just cut into the road with 20km/h (because they don’t yield at turn). The majority of the cars in Shanghai are still manual shift, and drivers have completely different skills since new drivers are of much higher portion in a fast increase auto car market, that caused the speed difference. The faster cars have to change lanes almost at every time it passes a car, to keep the same speed.

The lack of speed limit is also the reason. Some cars enjoy the freedom to drive much higher speed than required, making it hard to form a generally accepted speed.

Number of Lanes

Most of the roads in Shanghai have many lanes – Beijing has more, but compared to local roads in places like Silicon Valley, Shanghai’s main road have more lanes, to allow drivers to navigate from the left most, to the right most lanes

Road Design

The road design is also an important factor. To drive in Shanghai, you have to constantly switch lanes to get to your destination. There are more merges of lanes in Shanghai, and the buffer length left for the driver is short. You are forced to merge into another lane or change a lane. I have once tried to follow the way I drive in the States – choose a lane and stick to it. It is just impossible. It is generally much easier to drive in the Silicon Valley because of the planning of lanes to allow cars to stick to a lane as long as possible, and there are fewer merger, and a lot of fork. And there are a lot of signs to help drivers to merge (“THROUGH TRAFFIC MERGE LEFT”). That avoided a lot of last minute switching of lanes.


I believe in the future, when most of the reasons change, cars in China will follow the internationally accepted rules, and will not need to change lanes as frequently as now.

When the general quality of cars get better, and transit to auto shift, and the adoption of cruise (even for a small percentage of the cars), that may help to stablize the speed. Meanwhile, when the portion of new drivers (less than 5 years) go down, people will tend to choose the easiest, and less effort consuming way to drive, more people would not bother to switch lanes to get a little bit ahead of others, it should be OK.

For the road design, when the cars number reaches to a threshold that makes the optimization of the road system is economically feasible (build more ramps, build via-duct, and more signs), because the same change can benefit twice or more cars than today, that also help to avoid the need for drivers to change lanes.

I am a happy observer and thinking of all the small difference between my world and the world I am less familiar with, and most of the analysis leads me to be optimistic about the future of my world.

11 thoughts on “Frequency of Changing Lanes

  1. 沙发!!!


  2. I’ve being thinking about this as soon as I came back from a one-month visit in US this year. It is amazing how you analyze it, I cannot agree with you more. The South Yang Gao road is a typical one to observe. It has every problems you listed plus some large vehicles, big buses which need to frequently pull over at stops.

  3. The phenomenon is mostly due to the fact that the drivers in US are more mature about driving. Besides having more driving experience, they understand that following the traffic “flow” in lanes is usually the fastest and safest. It may also have something to do with the tendency of being eager for quick success and instant benefit in China’s society nowadays ;-)

  4. Right. When the society get more and more mature, people will tend to behave the same way to optimize for the general benefits. It takes time though. Like the situation we discussed here, cutting into lanes, no yield for straight traffic, and other behaviors helps individual but hurt the total system. It will take some time for this to get better – I am sure about it. Game theory proves that, but just need some time.

  5. i have 2 modes – shanghai mode and us mode. i still can’t drive easily in the rest of China – just too much stress – shanghai is much better than other cities in china.

    interestingly, when i say us mode, i’m thinking more about redmond and silicon valley. in fact, n.y./s.f. (and sometime even seattle) downtown are different, something between redmond and shanghai.

    i used to need about 1 or 2 days to switch between those 2 modes, now the moment i get out of the airport, i’m ready. :)

  6. It’s a great article, I have been thinking about the differences of driving situation in China and other advanced countries, I had been driving in the UK for more than 2 years by the way. I think the author has made some efforts on this topic, he analyzed this difference in three ways, but to be honest, the major problem I think is the way we are producing drivers and the Design of Roads. I suppose that we need more and more tight restrictions on becoming qualified instructors in driving cars and tighter system in testing those new-drivers, they do not only teach people to become a driver, more importantly they need to make sure their customers are to be a qualified safe-driving drivers. The road designer in China has to learn how their counter-partner in other countries design theirs, they have to obey the basic international rules, we have way too many merges in China without proper indications, or even has no reason to exist! So what I am trying to say here is, it’s been 7 years I came back and drive in China, I have driven to many parts of China, obviously you can expect better conditions in large cities than those small cities or countryside, but they are basically the same, I don’t agree some people say Shanghai is much better than other cities in China, whichever city I drove, either Shanghai or Guangzhou or somewhere else, you’d know that you are driving in China. As drivers, we have developed and improved skills and habits in driving these years as the number of cars expanding every year, but I don’t think the authority in driving has developed their ability of governance. It’s them who need to cope with the development of motor vehicle usage, they need to improve their knowledge in designing the roads under our feet.

  7. People from the Midwest or other rural parts of the US find Silicon Valley to be pretty stressful for driving.

    I think you guys are right, people in Shanghai are willing to take tremendous chances for little gain. Like, go into the oncoming lane to pass someone, but then have to immediately stop for the red light. Why?

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