Signal Spacing Studies
Evolution of Signal Spacing
Traditional Signal Spacing Calculations
RSI's Approach to Signal Spacing Calculations
Evolution of Signal Spacing
The introduction of articulated intermodal equipment and higher operating speeds has placed more demands on the rail industrys' current signal system. Some of these same signal systems were implemented when steam engines were in use. Continuous advancements in rail equipment and in track conditions have forced many railroads to evaluate their current signal spacing requirements more frequently.
Traditional Signal Spacing Calculations
Traditional signal spacing analysis uses a simple calculation to determine the safe stopping distance for a train between two approach home signals. Traditional analyses do not take into consideration significant operations variables. Operation variables can dramatically effect the actual stopping distance of the train. More sophisticated stopping distance calculations can ensure that the railroads' valuable capital is not wasted by re-spacing signals that actually provide sufficient stopping distance. These sophisticated calculations can confirm conditions of inadequate signal spacing that may be overlooked with traditional calculations.
Rail Sciences' Approach to Signal Spacing Calculations
RSI's advanced signal spacing model considers several operations' variables in order to determine accurate signal spacing requirements. Factors included in the RSI analysis are
● Train Length
● Brake Pipe Pressure
● Car Types
● Locomotive Brake Handling
● Change in Grade as the Train is Stopping
Specifically, Rail Sciences' Signal Spacing Model accounts for the propagation delay in air brake set-up, the cylinder pressure build-up, various feed valve pressures and types and timing of the brake applications. These variables, which are not considered in more traditional models, should be analyzed when making costly signal spacing decisions.
Rail Sciences can provide signal spacing studies that meets our clients requirements whether those requirements involve a complex systemwide signal spacing analysis or the development of a basic signal spacing table.
For example, RSI can perform a comprehensive review of system reliability and simulate the stop distance at each signal pair across a railroad system. RSI's automated methods simplify this comprehensive task and allow RSI to calculate signal spacing requirements for various train types (Coal, Doublestacks, Manifest), speeds, and/or tonnages. Or Rail Sciences can develop basic stop distance charts and/or tables as a function of tonnage. The railroad planner can estimate the grade factor, determine the speed, then extrapolate the predicted stop distance from the graph or obtain it from a table.
RSI has been involved in numerous studies to determine the maximum safe train speed for a given signal spacing, terrain, various types of trains and tons- per-operative brake. Determining maximum safe train speed has become particularly important with the increase in unit train tonnages to 286,000 pound loading. Intermodal equipment has also seen significant changes in tonnages and in types of equipment for intermodal trains resulting in a review of signal spacing requirements for this equipment.
