Bidirectional Crossing Predictors for Train Direction Discrimination
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Solution Overview
Problem
In densely populated areas with multiple railroad crossings, existing crossing predictors face challenges in reliably distinguishing train directions and managing frequency interference, leading to increased costs due to the need for insulated track joints and complex signaling systems.
Innovation Solution
Implementing bidirectional crossing predictors that communicate via vital I/O links or rail-based communications to determine train direction without insulated track joints, allowing for efficient DAXing (downstream adjacent crossing signaling) and reducing the need for unique transmission frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bidirectional crossing predictors are used to detect trains from both directions, then the ability to detect trains is improved, but the ability to distinguish train direction deteriorates
Solution Approach 1:
The patent introduces an intermediary communication system (vital I/O links or rail-based communications) between upstream and downstream crossing predictors. This intermediary enables the upstream predictor to receive direction information from the downstream predictor, allowing accurate direction discrimination without requiring the upstream predictor to independently determine direction from bidirectional signals alone.
2Reliability
If insulated track joints are installed to enable unidirectional signaling, then the signaling reliability is improved, but the system complexity and installation cost increase
Solution Approach 1:
The patent replaces the mechanical/physical insulated track joint system with an electronic/communication-based solution. Instead of using physical insulators to block signal transmission mechanically, the system uses vital I/O links or rail-based communications to electronically control and transmit directional information, thereby eliminating the need for insulated track joints while maintaining signaling reliability.
3Reliability
If multiple unique frequencies are assigned to adjacent crossings, then frequency interference is reduced, but the availability of frequencies is limited and system complexity increases
Solution Approach 1:
The patent extracts the frequency management requirement from the crossing predictor system by introducing a separate communication channel (vital I/O links or rail-based communications). This allows crossing predictors to share the same transmission frequency without interference, as direction and DAX information are transmitted through the separate communication channel rather than through the rail-based frequency signals.
4Ease of operation
If DAXing is implemented without direction determination, then downstream crossing signaling is simplified, but incorrect DAX activation may occur
Solution Approach 1:
The patent implements a feedback mechanism where the downstream crossing predictor provides direction information back to the upstream crossing predictor through vital I/O links or rail-based communications. This feedback loop allows the upstream predictor to accurately determine train direction and activate DAXing only when appropriate, preventing incorrect activation while maintaining operational simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the ability to accurately predict train arrivals at downstream crossings while reducing installation and maintenance costs by eliminating the requirement for insulated track joints and complex frequency management.
Implementation Method 1
the crossing predictor detects a train and determines its distance and speed by measuring impedance changes due to the train's wheels and axle acting as a shunt across the rails and thereby effectively shortening the length (and hence the impedance) of the rails in the circuit
Data Source
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AI summary
First and second crossing predictors communicate with each other, and each predictor transmits signals to instruct downstream adjacent predictors to activate their warning devices at a constant warning time (referred to as DAXing) by using train detection information from the other predictor. The communications between the predictors may be rail based, wireless or wired using conductors other than rails. Multiple predictors may be present between the first and second crossing predictors, and each such predictor may be DAXed by one of the outer predictors based on the train's direction. The predictor also transmits a signal to inform the other predictor of the presence of the train so that the other predictor may determine whether to suppress DAXing. Also disclosed is a method for detecting an incoming train direction at a predictor by utilizing a second receiver attached to the track rails at a location offset from the first receiver.