Abstract
Widely applied train location determination solutions in CTCS-3 (Chinese Train Control System, CTCS) and ETCS-2 (European Train Control System, ETCS) are Balises installed on the track. This solution causes a lot of efforts just to maintain these devices along the trackside. Train location determination through GNSS (Global Navigation Satellite System, GNSS), as moving the train location determination entity up to the trainborne side, reduces maintain costs on the track. However, GNSS performance is affected by the environment by multipath, shadowing and other effects. The GNSS signal quality at the receiver’s antenna is affected by these effects. The GNSS signal in space (SIS) quality does not take signal in ground environment (SIE) quality into consideration. Transportation systems like railway are actually the end users of GNSS. The SIE quality is more important than SIS for end users. Different level of GNSS performance derived from the GNSS SIE quality shows the capability of GNSS-alone applications. This paper links the GNSS accuracy performance with the railway safety concept. The GNSS accuracy degradation due to the environment scenario is categorized at first. The quantification parameter for scenario categorization is estimated using the accumulated error density function plot with threshold values. The error sources to each environment scenario is analysed in order to allocate the hazardous event sources. After that, the degradation to hazardous event is deduced using formal method as Petri net to estimate the hazardous event sequence. With the sequence, and the established stochastic Petri net, the probability of the hazardous event linked in the environment scenario is analysed. The data for the error estimation and probability calculation is collected along the Qinghai-Tibet railway line using an experimental vehicle. The results will include both real and simulated GNSS data to analyse and validate the given conclusion in this paper.
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