The reason I love business world is, you have to reach a level of excellency in digging into details of all the aspects of your business to really be able to deliver a world class product or services. I tend to practice this skill in worlds other than business. Transportation of large cities is one of the area I spent a lot of time thinking. Here is one of my observation.
Smaller Road Blocks Leads to Better Transportation
I have the gut feeling that the smaller the blocks are, the better the transportation is. Examples are Puxi vs Pudong, or Shanghai vs Beijing. Puxi has much more cars than Pudong, and Beijing has much more big roads than Shanghai, but the Puxi is better in transportation than Pudong, and Shanghai is better than Beijing. Why? When I tried to verify this conclusion and to find the reason, I found some insights. One of them is the importance of right lane.
Right Lane is the Most Important Lane in a City
I thought all lanes are created equal – because they are equal in terms of width. But they are not.
I found this because of the Huashan Road construction. The Huashan Road is the road before my office. It is a main road that goes to Xujiahui on the south. There are 5 lanes at the crossroad with Hongqiao Road. One left lane, one left/forward lane, two forward lanes, and one right lane. The traffic is heavy but for many years, it went on well.
All of a sudden, one day, the whole Huashan Road is blocked. The long queue of cars line from Hong Qiao Road to Guangyuan Road (that is about 1 km long), and extends to Huahai Road (about 1.5 km long). Cars are jammed there, all the day time. From my window, I can see the long line, and hear continous horn from impatient drivers. If you thinking about 2KM queue, and there are 4-5 lanes on the road, you can imagine how many cars are impacted daily. Even buses detoured from this section of road.
What happened? Is there a big change?
Nothing except they closed a right lane at Huahsan Road and Hongqiao Road, and merge it into the straight lane, becaues of the Xujiahui Metro Station construction at Grand Gateway.
Right Lane Multiplied by Time
It is a shocking discovering for me. Before, I thought a right lane = 1/5 of the traffic. It turned out to be the wrong assumption. The key characteristic of right lane is, cars are allowed to turn right ALL the time – at greent light and red light. Cars at forward and left lane have to wait for red light to really “use” the lane to move. What is the percentage of time they can see green light?
At a crossroad of equally important two roads, if there is no seperate left turn light, each side can only use 1/2 of the time. However, that is the whole story. Since the left turn and forward traffic needs to wait for each other, the lane actually is used 1/4 of all the time (assuming left turn and forward are of the same traffic). If there is seperate left turn light, the forward is actually 1/4 of all the time.
Meanwhile, no matter what time it is, the right lane is always available. In a crossroad like Huashan Road and Hong Qiao Road, the utilization of right lane is almost 100% during day time (unlike most other crossroads). The conclusion is, a right lane can archive traffic 4 times as a left or forward lane under full utilization senario.
If the right lane is combined into the forward lane, right lane cars have to wait for the 1/4 of the green light, effectively decreased the output of the road – 3/4 of the traffic capacity is cut.
That is the secret why reducing 1/5 of the lanes causing the capacity to drop to almost half. If you take the capacity of an always green light road to be 1, previously, it was 2 (1 + 1/4 * 4), and now it is 1.25 (1/4 * 5), a 35% decrease.
This translate to the long queue of roads.
Right Lanes and Road Grid
When there are more smaller roads and smaller road grid, the key is, there are much more right lanes than big road system. Like highways, although there are many forward lanes, right lane per km is much less than smaller road system. If it makes sense for expressways to build large road system, it does not apply to cities like Beijng and Shanghai.
With right lanes, the road utilization is increased, because cars can choose to make right turn if they can, and causing less cars on the forward lanes. Meanwhile, right lane cars fills into the empty road when there is red light at the crossing road. In a road grid of many right lanes, the ratio of cars and road area is much higher (higher utlization), and causing a more efficent road system.
P.S. I enjoys learning insights of things like this a lot, just the same way as I run my business. Many people can do the same thing, but only few people really know what they are doing. The excellence of understanding is what I am chasing after.
P.S. 2. It also shows the power of convinience and the meaning of keep doing for a long time. Many things looked alike, if you don’t take the accumulation of time into account, but it is the time factor that makes something so unique. Like business, many companies look alike, but only very few of them can focus on what they determined to focus on, and keep doing it for a long time. That is huge difference.
you are right on this one. I’ve noticed this a while ago (金都路上A4的口), but you explained it great!
Contrary to what we’ve been taught, intelligence is very important. Traffic cops are watching the traffic all the time, and their job is to keep the traffic flow. How many of them can come up with an explanation like this. Looking at many of the traffic lights, road signs, and lane divides in Shanghai, you can’t help but wondering, how stupid a person has to be to design a system like this.
Jianshuo, your analysis is very clear. But I fear it’s somewhat limited to China, because in many or most other countries (maybe others can jump in), right turns are much more restricted. At the least, most other places require that right turns stop first and yield to oncoming traffic, so the proportion of traffic the right lane carries will be proportionately less. In some places, for example New York City, right turns are only allowed on green, so the right lane carries the same amount of traffic as the other lanes.
@ddjiii, yes. In countries like US, you need to yield or full stop before turning right. And before that, I always cannot remember whether right lane traffic should yield to left turn or U-turn or the other way. Now I understand why they make that rule (this rule is there because of a reason). Just because right lane has 100% of the time, but forward, left turn or U-turn just have 1/4 of the time share, reducing the right lane actually balance the traffic, because the scarce resource in a road system is the time available for forward, and left turn traffic, and right lane traffic is always proportionally more than others.
My belief is, not just follow the rule like “full stop before turning right”, think about what is the reason behind it.
Are there pedestrians on these intersections?… in many cities in US, streets are much smaller comparing to streets in Shanghai and Beijing especially in downtowns. I often feel the right lanes can be the slowest lanes in such areas… because you have to give pedestrians the right of the road first. In some cities you have to wait till the pedestrians are safe which means two lanes distant away from the curb. I think “pedestrian” is one of the main reasons for “full stop before turning right”.
GN, yes there are many pedestrians on those intersections but here in China no car will give right of way to a pedestrian. That is why this rule of right turn can go no matter what colour the light is is very annoying for pedestrians. You can never cross the road here without a care.
I do know it is more difficult to manage intersections in China… simply, too many people. What I am getting to is that if those intersections WJS was talking about were with pedestrian cross lanes, there are many intersections are with overhead “bridges” and underground tunnels in China… haven’t seen one in US, then it would be hard to say that right lanes are the most important/best lanes by design.
Very insightful. I had not thought about this much but you sure make a lot of sense here. I live in the Phoenix area and our streets are laid out in a grid so it’s pretty easy to get around. The worst cities in the US may be Boston and San Francisco. I’ve driven in both and Boston is a nightmare. The tradition is that in Boston they just put down the streets to follow the cowpaths that were all over the place in the 1700’s. Boston streets are just a bunch of triangles. By the way, what is your opinion of intercity flyovers? No trucks or busses over these. Just cars. Do you think these would work if they were standardized and built quickly? I bet Chinese engineers could find a way do do this real well.
– Leon….Mesa, Arizona