In China's highway transportation, the types of semi-trailer can be said to be diverse. Have you ever heard of or seen a child parent semi-trailer? Strictly speaking, the child parent semi-trailer is not a vehicle type, but a vehicle operation mode. The specific principle is that both vehicles only transport one-way goods. When the empty vehicle returns, one vehicle returns with the other vehicle on its back.

In fact, child parent semi-trailer has been widely existed in the early years. Ten or twenty years ago, when the network was still underdeveloped, car owners could only obtain the distribution information by offline means. It was very difficult to find suitable goods in unfamiliar areas, so many times the vehicle had to choose no-load on the return trip. In order to minimize operating costs, car owners thought of this way of "back car". At that time, there were businesses dedicated to "back car" in some regions.

A few years ago, in the coal transportation industry, this kind of child parent semi-trailer rose again, especially in the long-distance coal transportation. After the semi-trailer charges by axle, the cost of empty vehicle return increased, and many teams began to choose the mode of child parent vehicle to reduce the comprehensive cost.

At this time, the sub parent semi-trailer has made a new design compared with the past. In addition to the more reasonable planning of the top and height of the parent vehicle and the sub vehicle, other aspects have also been improved. For example, the parent vehicle selects the high roof double sleeper cab, which can facilitate the driver of the sub vehicle to rest, and the sub vehicle selects the flat roof lightweight cab, so as to deal with the height limited road section and reduce fuel consumption.

As for the operation advantages of child parent semi-trailer, it is also obvious:

1. Save the road toll, fuel cost and related expenses on the return trip. According to the relevant investigation, under the condition of 1500km, the fuel cost can be saved by about 800 yuan, the toll can be saved by about 1400 yuan, and the costs such as parking fee and tire damage can also be reduced.

2. Reduce labor costs and improve operation efficiency. Under the "car on the back" mode, three drivers are generally selected for attendance through the circular system. Compared with the previous method of employing two drivers for one vehicle, it can reduce some labor costs, ensure the safe sleep of drivers and improve operation efficiency.

In this way, it seems that the child parent semi-trailer does have a certain effect of reducing cost and increasing efficiency, but is this "back car" worth advocating? Let's first analyze several problems:

1. Not suitable for all logistics scenarios. The child bus trailer is suitable for the special market with full load and empty return, such as coal transportation with fixed and paired lines, or remote lines with large inflow and small outflow. For those retail car owners, it seems not so easy to find two semi trailers with the same source of goods and the same route;

2. Transportation safety issues. Especially after the combination of the parent vehicle and the child vehicle, the child vehicle itself belongs to an indivisible large cargo, and its contact area with the parent vehicle is relatively limited, and the friction force is too small. It's OK to say if the parent vehicle is designed with special fixing tools, otherwise, once the emergency brake is encountered in the transportation process, the child vehicle is easy to displace due to inertia, affecting the driving safety.

3. Operational compliance. In fact, the sub parent semi-trailer is also a "loophole" product. According to the requirements of laws and regulations, the transport auxiliary vehicle must use a special flat car. At present, there are no clear laws and regulations that allow or stipulate that the sub parent semi-trailer can drive on the road, and the "car on the back" mode may have problems such as superelevation and overweight.

Therefore, the "back car" method of child parent semi-trailer is just a helpless move taken by car owners under the condition of depressed freight, which is not worth promoting, but there are also exceptions in special markets. For example, professional logistics companies, in a fixed transportation line, design special semi-trailers, one large and one small, in strict accordance with the legal size requirements, start in pairs, and carry small cars on the back of the big car on the return trip. Another example is the transportation of new cars. The parent car is a low flat semi-trailer, and its chassis is much lower than that of ordinary semi-trailer. Generally, it can transport the tractor head or small passenger car to realize the "back car".

It is worth noting that under the "back vehicle" mode, the requirements for the stability, vehicle center of gravity and vehicle weight of the main vehicle are higher. Choosing the right axle and suspension will naturally get twice the result with half the effort. Darong group has been deeply engaged in the trailer axle industry for more than 20 years. Its disc axle, drum axle, low flat axle, concave axle, three-line six axle axle axle, air suspension and other products are rich and diverse. Its process, technology, experience and strength are reliable and can meet the diversified use needs of users.