Four-Quadrant Gated Crossing

Printer Friendly Version

Title: Four-Quadrant Gated Crossing

Phase(s): Construction

Category: Scope

Date: September 13, 2000

1. Background

On September 29, 1997, the Massachusetts Bay Transportation Authority (MBTA) successfully completed the rehabilitation of the Old Colony Railroad Rehabilitation (OCRR) Lines. This commuter line restored rail service to 32 South Shore communities between Braintree and Plymouth/Middleborough areas. The OCRR services an area covering nearly 450 square miles and is comprised of approximately 70 miles of track, 44 signalized grade crossings and 15 stations. Today, the local roads, which accommodate more automobiles, have trains traveling at speeds up to 70 miles per hour passing through the highway-rail grade crossings nearly every hour throughout the day.

Aware of concerns for public safety, the Commonwealth of Massachusetts passed legislation in 1996 in an effort to attain a higher level of safety at the newly activated crossings along the OCRR. Prior to instituting the changes called for in the legislature, the MBTA applied for and received a grant from the Federal Transit Administration (FTA). The grant was awarded to demonstrate four-quadrant gate operations on the OCRR and then evaluate its effect on or enhancements to system safety. The MBTA commissioned a private consulting firm (SYSTRA) to establish, implement and evaluate design methods for four-quadrant gated grade crossings with Vehicle Intrusion Detection System (VDS).

The project involved participation from various Federal and State agencies including: the FTA, Federal Highway Administration (FHWA), Federal Railroad Administration (FRA), MBTA, Department of Energy and Telecommunications (DTE), and the American Association of Railroads (AAR) as well as Amtrak and the Town of Abington. Early involvement by all the referenced parties resulted in the successful implementation of this demonstration project.

In order to develop a safety optimizing four-quadrant gate design that optimizes the safety offer a highway-rail grade crossing, the operating characteristics of both modes of transportation were thoroughly studied. MBTA's design consultant conducted a detailed corridor analysis of each of the newly constructed 44 signalized highway-rail grade crossings along the OCRR before installing the four-quadrant gate system. This analysis focused on enhancing warning systems at each crossing. The existing arrangement of the warning devices were documented and evaluated specifically for this investigation. This systematic approach ultimately helped to determine where the four-quadrant gates could be installed for the greatest public benefit.

The final design step was to select one of the existing highway-rail grade crossings on the OCRR for the demonstration project. Wales Street in Abington met all the parameters of the design methodology. Additionally, baselines of motorists' behavior could be established, as well as the associated costs for the four-quadrant gate system could be estimated for other applications of highway-rail crossings in the Commonwealth of Massachusetts.

Prior to the construction of the four-quadrant gate system at Abington, cameras were installed at the Wales Street crossing to observe its current operation and driver behavior patterns. The camera recorded each event until the warning system was no longer activated. The MBTA reviewed the recorded videotapes every few days and any incidents or right-of-way violations were identified and logged. For purposes of this study an "incident" was defined as any automotive vehicle, pedestrian, or bicyclist that violated the existing warning devices and proceeded through the crossing after the initial bells, flashers and gate arms were activated. The base line survey was conducted for an eight-week observation period from May 26, 1998 to July 15, 1998. During this time period the MBTA documented thirteen incidents.

Following the baseline observation period the MBTA preceded with the installation of the four-quadrant gate design elements. The design elements were comprised of the following components:

  • Raised Concrete Median Islands
  • Gate Offsets
  • Emergency Exit Zones
  • Signage and Striping
  • Exit Gates
  • Vehicle Intrusion Detection System (VDS)
  • In-service testing
  • Public Awareness

The concrete median islands (7 inches in height) provided channelized traffic control for vehicles entering and exiting the crossing area. With a target distance of 25 feet from the gage of the rail, this offset gate allowed the motorist who managed to pass the entrance gate just before it descended to leave the crossing area. The off set gates provided strong visibility relative to the no crossing zone once the system was activated. Emergency exit zones were created to provide for an emergency pull off area should the motorist panic during the system activation process and become restrained between the entrance gate and the off set gate once the system responded to a train approach. Signage and striping was implemented to warn both pedestrians and motorists of the different types of railroad crossings. The exit gates themselves provided the basis of the four-quadrant gate system to prevent motorist from intentionally circumventing the standard gate warning devices. The Vehicle Intrusion Detection System was designed and installed as a non-vital element of the railroad grade crossing signal system and was to have minimal interface with the vital signal system. The VDS was outlined in each vehicular travel lane and designated as the Zone of Detection (ZOD). The ZOD was effectively located between the entrance and exit gate for each lane of traffic and was comprised of fluxgate magnetic sensor (magnetometers) elements placed strategically within the designated ZOD and connected to the exit gates via electronic signals. The magnetometers measured a change in the magnetic field of the earth detected by the presence of a vehicle located within the ZOD. The VDS was designed to not be ignored or shut off by the vital circuits controlling the exit gates signal system as the train passed through the crossing. Once the system was installed and tested an in-service observation period was conducted for approximately 26 weeks from June 18, 1999 to December 18, 1999 and then extended to mid March 2000 to provide further evaluation during inclement winter weather conditions.

During the entire process public awareness and "Operation Lifesaver" played a crucial role in the overall effectiveness and success of the program. The MBTA extended the "Operation Lifesaver" program to local schools and heightened public awareness about the four-quad gate program. Through educating and communicating with the public officials in the Town of Abington, the MBTA was able to develop a strong partnership that provided support for the demonstration project. In addition, the MBTA worked with a local television station and developed two special video programs regarding the four-quadrant gate system for educating the public.

2. The Lesson

During the demonstration project there were two events recorded that indicated a problem with the operation of the crossing. Both of these events were minor in scope and required only slight adjustments to the elements of the four-quadrant gate system. Based on the evolution of the project the following lessons were learned for possible future applications.

  • Exit gates that require to be powered down and remain under power to stay down will require a dedicated 12VDC vital battery source. Future applications should investigate gate manufactures prior to design for requirements regarding the power down and stay option of the gates once the system would be activated.
  • The location of the magnetic sensors is critical to the overall performance and reliability of the VDS. It is recommended that a detailed site survey at any future crossings be performed in order to establish a thorough understanding of the normal magnetic field that exists when a train is passing through the crossing.
  • During the preliminary testing, it was determined that two sensors should be installed in the track bed approximately fifteen feet outside of the crossing area. This would greatly reduce the complexity of the algorithms the controller would have to analyze, especially with slow moving trains or equipment movements through the crossing.
  • It is recommended that if an emergency exit zone is provided, an additional sensor should be located at approximately eight feet back from the existing sensor located in the street. The purpose of this is to provide positive directional identification of a vehicle that enters the area, either as an escape route during a train event or as an unauthorized entry.
  • Sensor cables should be constructed flush and plumb with the track bed in accordance with the installation drawings for maximum effectiveness and reliability.
  • Sensor cables should never be spliced in wet weather or unsuitable soil conditions as this may result in system failure and erratic behavior. Also, sensor cabling should be comprised of double-jacketed railroad burial grade, as it is far more durable and effective for use in the critical nature of grade crossings.
  • Should four-quadrant grade crossings be installed and placed into extended service, a maintenance plan and schedule needs to be developed and implemented consistent with current AREMA standards and CFR 49 requirements.
  • Large induced currents, such as those caused by the Sperry Track Inspection Car, used to test weld integrity in the track, caused a residual magnetic effect in the reinforcing bars of the concrete ties. This dramatic change to the magnetic ambient conditions along the track will necessitate a need to re-baseline the sensor array to compensate for such an altered condition.
  • A four Quadrant Gate system cannot be applied or "forced" at all crossing locations. Each location has its own merits and concerns and a detailed systematic review is required to determine the best way to address the crossing.

3. Applicability

The four-quadrant gate system demonstrated that new technology combined with traditional grade crossing applications and enhanced feature elements could be effective and reliable to control motorist movement at an activated highway-rail intersection. However, this project demonstrated that a four-quadrant gate system cannot be applied or "forced" at all crossing locations. Each highway-rail grade crossing under consideration for a four-quadrant gate system must be thoroughly evaluated by a team of experts who can assess the unique site characteristics and specific configuration of the proposed crossing and highway geometry. This demonstration has shown that a four-quadrant gate system can be added to an existing operating system. Further, this project has demonstrated the need for additional testing of the new VDS technology utilizing magnetometers as well as industry evaluation. Other viable alternatives, such as the extension of gate arms and the use of roadway medians should be considered during the preliminary engineering phase of the project.

4. References

  • Four-quadrant Gate Demonstration Project on the Old Colony Railroad
  • Design Methodology Report (Draft final report Rev. 1 June 2000)
  • Corridor Analysis Report- April 1998
  • Manual for Uniform Traffic Control Devices (MUTCD)
  • Operation Lifesaver
  • Specialized Pamphlets for Public Education "Operation Lifesaver”
  • Video Programs Developed for Televised Education in the Local Community

A A A    Bookmark and Share