Aerospace and Electronic Systems Magazine May 2017 - 4

Feature Article:

DOI. No. 10.1109/MAES.2017.150104

Collision Avoidance Radar System for the Bullet Train:
Implementation and First Results
Aihua Liu, Qiang Yang, Xin Zhang, Weibo Deng, Harbin Institute of Technology,
Harbin, P.R. China

INTRODUCTION
Bullet trains greatly improve railway transportation capacity because they travel at amazingly fast speeds on specially designed
high-speed railways. These trains are designed to travel at speeds
as high as 400 km/h. As traveling speed increases, the ability of the
emergency braking system on the bullet train has to be enhanced
so that the train can stop in emergency situations such as signal
failure in a railway communication system or rock slides blocking
the railway. Bullet trains usually travel in two directions between
two railway stations on parallel tracks. Bullet trains traveling in
the same direction are supposed to run on the same track. In China,
an automatic blocking technology supported by the complicated
railway communication system is used to avoid collisions by keeping the bullet trains isolated from one another in different sections
of the railway. However, this kind of technology is not capable of
providing the driver with the exact positions of other bullet trains
or of discovering obstacles on the track ahead. When a signal failure happens, a bullet train may wrongly run into a section of railway occupied by another bullet train. If the bullet train entering
the railway travels faster than the bullet train ahead, a collision is
likely to occur because the driver of the second bullet train does
not have enough time to stop the fast-traveling train after he sees
the train ahead and realizes a collision is impending. This was the
main cause of 34 deaths in the "7.23" Yongwen line train crash that
happened in China in 2011. In addition to the sophisticated railway
communication system, it is important to equip bullet trains with a
technology that will allow the drivers to monitor the condition of
the railway their train is traveling on. The unique collision avoidance radar system for the bullet train presented in this article is
called CA radar. The CA-radar system is designed to be mounted
on the head of the bullet train, can provide the driver with real-time
information about the track ahead, and can allow that driver to detect obstacles on the track. It will work well under all weather conAuthors' current address: A. Liu, Q. Yang, X. Zhang, W. Deng,
Department of Electronic and Information Engineering, Harbin
Institute of Technology, Nangang Qu, Xidazhi Jie, Xinjishu lou,
807shi, Harbin 150001, P.R. China, E-mail: (yq@hit.edu.cn).
Manuscript received June 26, 2015, revised January 18, 2016,
and September 13, 2016, and ready for publication September
21, 2016.
Review handled by D. O'Hagen.
0885/8985/17/$26.00 © 2017 IEEE
4

ditions, day and night, at distances of several kilometers, ensuring
a final line of defense for the bullet train against collision events.
CA radar is an important branch of radar technology application in civilian sectors. It has received considerable research and
attention with promising results in cars [1]-[4], unmanned aerial
vehicles [5]-[7], planes [8]-[10], and other transportation systems.
Compared with other transportation systems, the bullet train runs
on a specially designed high-speed railway with more complicated
circumstances: there are always many buildings beside the track,
and catenary poles with uniform spacing are installed along the
high-speed railway to provide electric energy to the bullet train.
The distance between the catenary poles and the track is always
small, as shown in Figure 1.
When designing a CA radar, several principles need to be followed. These include the following:
1. The system should be active at a range larger than the maximum breaking distance of the bullet train. A detecting range
of 3 km is sufficient for the CA radar to prevent a collision,
because the bullet train usually travels at a speed of 300 km/h
with a maximum breaking distance of 2,700 m [11]. The system also should have high range resolution to separate items of
different distances.
2. Antennas installed on the train should not increase the aerodynamic drag for the high-speed bullet train.
3. Velocity estimation should be provided for the prediction of a
coming collision, and targets with different speeds should be
separable.

Figure 1.

Image of a typical high-speed railway.

IEEE A&E SYSTEMS MAGAZINE

MAY 2017

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