Trailer is one of the main models in the logistics and transportation industry, such as semi-trailer, full trailer, center axle trailer, etc. at present, semi-trailer is widely used in China, which is composed of tractor and a semi-trailer carriage. With the continuous improvement of vehicle technology, more and more new models are widely used, such as double trailers.

At first glance, this title seems to have a little unclear and sharp meaning. Double trailer, whose scientific name is double trailer train, continuously tow two standard semi trailers behind the standard tractor, or tow one standard semi-trailer and one center axle carriage. Among them, the rear of a semi-trailer at the front has been transformed accordingly to tow the semi-trailer car or middle axle car at the rear.

After reading the picture, many people said: why does this model look familiar? Isn't this the car that has been refitted privately before?

Yes, in the early years, the relevant laws and regulations on vehicles were not perfect, and it was common to refit models privately. This kind of model similar to double Trailer did appear, but the laws and regulations never recognized its legitimacy, let the traffic police catch it, and deduct points for fines, but there was no business.

It is understood that at present, this double trailer is used on the ground in many countries. In Sweden, Finland, the Netherlands, Spain and other countries, the standard connection mode is tractor + 13.6m standard trailer + Trailer connection platform + 13.6m standard trailer. The total weight does not exceed 72t, with a total of 11 axles. The average axle load under full load is about 6.5T. Compared with an ordinary semi-trailer with a gross weight of 40t, the average axle load is reduced by about 1.5T.

In contrast, in China, in recent years, users' pursuit of transportation loading capacity and timeliness has been continuously improved, resulting in the frequent occurrence of super large and super long vehicles in the transportation market, which neither meets the requirements of laws and regulations, nor is it difficult to realize standardized management, which is not conducive to driving safety. However, the double trailer is limited by the "maximum allowable total mass of vehicles is 49 tons, the maximum total length is no more than 16.5 meters, and the total length of automobile trains is no more than 22 meters" stipulated in gb1589, which has not been applied.

Compared with ordinary Trailer models, what are the advantages of double trailers?

1. Compared with ordinary towing and coupling combination, the transportation volume of double trailer can be increased by 50%, and the average transportation unit cost of various comprehensive cargo combinations can be reduced by about 34%, which greatly improves the transportation efficiency;

2. By using the double trailer transportation mode, the unit fuel consumption of transported goods can be reduced by 10%, the transportation cost is also reduced, and the road space is released to a certain extent;

3. In addition to commercial benefits, the environmental and social benefits brought by double trailers are also very significant, which can help reduce carbon dioxide emissions, reduce road surface wear, alleviate the shortage of drivers and so on.

Although double trailers have obvious advantages in transportation, they also have many shortcomings or shortcomings:

1. Needless to say, the extra danger brought by too large total mass is that the body is too long, the weight is too large, the driving is more difficult, and the lethality can not be underestimated. It is also because of this that the vehicles involved in the transportation of double trailers abroad must be equipped with hydraulic retarder, full vehicle air suspension and disc brake. At the same time, they must be equipped with perfect mechanical and electronic auxiliary systems, such as blind spot monitoring, adaptive cruise, electronic stability system, etc.

2. Transportation roads are restricted. After all, most of the entrances and exits of expressways, roundabouts and curves can not meet the transportation needs of double trailers, and vehicles may face the problem of difficult steering. In addition, many service areas or gas stations cannot provide extra long parking spaces. If double trailers want to park, they may have to uncouple and park separately, affecting the transportation efficiency.

3. The driving difficulty is too high. Compared with ordinary semi-trailer, the driving difficulty of double trailer is greater. Therefore, the requirements for double Trailer drivers abroad are also very strict. They must have five years of truck driving experience, have no accidents for three consecutive years, and must receive training before driving. In addition, when driving a double trailer, it is required to prohibit overtaking in the whole process and driving in harsh environments such as heavy rain and snow. The length of the vehicle must be marked at the rear of the vehicle, and reflective strips and warning signs must be installed.

However, according to insiders, the plan to realize the demonstration application of double trailers in some parts of China during the 14th Five Year Plan period is mainly based on four considerations:

1. The road transportation volume is large, and the task of energy conservation and emission reduction is heavy. At present, the freight volume of highway transportation accounts for more than 70% of the comprehensive transportation system. Coupled with the continuous development of express industry, the demand for large volume transportation vehicles is increasing day by day. In addition, the pressure of energy conservation and emission reduction is huge, and there is a long way to go to achieve the goal of "double carbon";

2. Non standard models are eliminated, and alternative models need to be supplemented. At present, the management of non-standard models by relevant departments is continuously strengthened, and the transportation industry urgently needs to supplement alternative models to alleviate the actual demand of the industry for high-capacity transportation;

3. The use technology and experience of international double trailers are rich enough to provide a good reference experience and learning basis for domestic research;

4. At present, China has become a party to the United Nations Customs Convention on international transport of goods with TIR certificate, which not only promotes the facilitation of China's international road transport, but also promotes the integration of domestic models with international models. It is urgent to improve the types of road transport vehicles in China.

It can be seen that the application of double trailers in China will take some time, and may become a legal model on the road in the near future. According to relevant foreign experience, the installation of disc brake and air suspension for double trailers may become standard. Darong heavy industry group is one of the enterprises that started earlier in mass production of "one-piece" axles in China. Founded in 2001, it focuses on the R & D and production of various trailer axles, axles and accessories. Darong's disc axle was independently developed and produced in 2018 and successfully entered the market. It adopts lightweight materials and integrated alloy brake discs, combined with locally strengthened square axle beams, trailer special bearings and other accessories to improve the bearing capacity, Successfully reduce the axle weight and fully save fuel and increase efficiency. The price of Darong 13T standardized disc axle is about 6500 yuan, and customized services can be provided for special sizes.