Chapter 1: Introduction

General

Traffic signal railroad preemption is defined as the transfer of a traffic signal’s normal operation to a special timing sequence prior to the arrival of a train when a grade crossing is located near a signalized intersection. The purpose of this manual is to provide the appropriate tools, guidance, and standards regarding railroad preemption systems, design, implementation, and maintenance throughout the State of Texas. When railroad preemption is properly installed, motorists are able to safely and efficiently maneuver through grade crossings as well as the adjacent interconnected signalized intersections. Throughout this manual, railroad preemption
is referred to as preemption
.

Manual Organization

This manual is organized in three main topics to describe the overall preemption process. Chapters 1 through 3 define various aspects of preemption and guide readers to a better understanding of each element involved. Chapters 4 through 7 describe the different design elements and proper implementation of preemption. Chapter 8 discusses the traffic signal and railroad maintenance procedures and responsibilities of the relevant stakeholders.

Chapter 1, Introduction
, describes the purpose, common definitions and abbreviations, and existing technical references applicable for this manual.

Chapter 2, Identifying the Need for Preemption
, describes how to determine if preemption is needed at a specific location and potential preemption operations.

Chapter 3, Preemption Time Calculations
, describes how preemption timing parameters are calculated and how said parameters can determine and affect the overall railroad approach time needed at grade crossings.

Chapter 4, Railroad Relays and Systems
, describes railroad relays – including various types, functions, and applicability. It also discusses preemption request forms and limitations of the railroad equipment to consider when implementing preemption.

Chapter 5, Equipment Standards
, describes components within traffic signal cabinets and their interface with the railroad equipment during preemption.

Chapter 6, Interconnected Crossing Design
, describes design techniques, strategies, guidance, and standards on how to design at grade crossings with traffic signal interconnection.

Chapter 7, Construction and Implementation
, describes the preemption implementation process and defines the responsibilities of TxDOT and the appropriate railroad authority as related to traffic signal interconnection.

Chapter 8, Inspection and Maintenance Considerations
, describes the necessary inspection and maintenance processes to identify and troubleshoot the quality and functionality of existing preemption operations.

Existing Technical References

Table 1-1 below lists various technical documents that provide industry standards and recommended practices and are referenced throughout this manual.

Table 1-1. Technical Standards and Guidance
Technical Reference Name	Agency	Year Published
AREMA Communications and Signals Manual¹	AREMA	2025
ITE Preemption of Traffic Signals Near Railroad Crossings	ITE	2021
Traffic Signals Manual	TxDOT	2020
FHWA Railroad-Highway Grade Crossing Handbook	FHWA	2019
Form 2304 and 2304-I	TxDOT	2019
Form 2625 and 2625-I	TxDOT	2023
Rail-Highway Operations Manual	TxDOT	2023
ITE Traffic Control Devices Handbook	ITE	2013
Texas Manual on Uniform Traffic Control Devices	TxDOT	2025
At-Grade Intersections Near Highway-Railroad Grade Crossings	TxDOT	2001

¹Note this manual is updated annually

Abbreviations and Definitions

Table 1-2 below lists the common abbreviations used throughout this manual. Other more specific abbreviations will be defined later in the appropriate chapters.

Table 1-2. Common Abbreviations
Abbreviation	Term
APT	Advance Preemption Time
AREMA	American Railway Engineering and Maintenance-of-Way Association
CFR	Code of Federal Regulations
ERT	Equipment Response Time
FHWA	Federal Highway Administration
FRA	Federal Railroad Administration
ITE	Institute of Transportation Engineers
MT	Minimum Time
TMUTCD	Texas Manual on Uniform Traffic Control Devices
TxDOT	Texas Department of Transportation
RRD-RSS	Rail Division-Rail Safety Section (TxDOT)
RRD	Rail Division (TxDOT)

Table 1-3 lists some common definitions used throughout this manual. Other more specific definitions will be defined later in the appropriate chapters.

Table 1-3. Common Definitions
Term	Definition
Grade Crossing Warning System	The flashing-light signals, with or without crossing gates, together with the necessary control equipment used to inform road users of the approach or presence of rail traffic at a grade crossing.
At-Grade Crossing (Grade Crossing)	The general area where a highway and a railroad and/or light rail transit route cross at the same level, within which are included the tracks, highway, and traffic control devices for traffic traversing that area.
Diagnostic Team	A group of knowledgeable representatives of the parties of interest in a grade crossing or group of grade crossings (see 23 CFR Part 646.204). A railroad company signal maintainer, local government representative, and FHWA or FRA representative are also included as needed (TxDOT Rail-Highway Operations Manual, pg. 4-9).
Highway Agency	Agency that owns or has jurisdiction over the relevant highway or roadway. The Highway Agency may be TxDOT or a local agency (City or County).
Interconnected Railroad Crossing	A railroad at-grade crossing which has an electrical connection between the railroad signal system and a traffic signal system for the purpose of providing preemption.
Railroad Company	Railroad company that owns, maintains, and/or operates at the relevant railroad grade crossing. Note: There may be multiple railroad companies at a given grade crossing.
Traffic Signal Interconnection	The electrical connection between the railroad signal system and the traffic signal system for the purpose of providing preemption.

General Roles and Responsibilities

Table 1-4 details the roles and responsibilities of each typical stakeholder within this manual. Other more specific responsibilities will be defined later in the appropriate chapters.

Table 1-4. Titles and Roles/Responsibilities
Title	Role/Responsibility
TxDOT District Railroad Coordinator	Responsible for coordinating with the railroad regarding diagnostic meetings, joint maintenance inspections, and any grade crossing-related incidents. Also responsible for coordinating with local highway authorities regarding any construction work taking place near grade crossings including controller testing and cutover.
TxDOT District Traffic Engineer	Responsible for general traffic engineering within the District. Also, regarding interconnected crossings, responsible for coordinating annual joint maintenance inspections and being the primary point of contact for issues noted outside annual inspections. These responsibilities may be delegated to another qualified person.
Diagnostic Team	Group consisting of the railroad authority, highway authority, and project team to visit the project location and discuss the existing conditions as well as any proposed improvements. The role of the diagnostic team specific to interconnected railroad crossings is discussed further in Chapter 2 of this manual, with additional details provided in the TxDOT Rail-Highway Operations Manual.
Highway Agency	Owner of the roadway. For the purposes of railroad preemption, the agency responsible for maintaining the traffic signal.
Railroad Company	Owner and/or operator of the railroad line. For the purposes of preemption, the railroad company is responsible for maintaining the railroad warning devices and railroad circuitry.
TxDOT Railroad Investigators	Railroad investigators are not required to attend inspections; however, relevant information should be shared with them. Railroad investigators may participate in cutovers and diagnostic reviews, if necessary.
TxDOT Rail Division (RRD) Representative	Has the authority to implement rail improvements through public-private partnership agreements and provide investments in freight rail relocation projects, rail facility improvements, rail line consolidations, or new passenger rail developments. Provides guidance related to the railroad interconnection implementation process. This individual should be invited to maintenance meetings but is not required to attend.

Railroad Preemption Manual