U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
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Currently, the technology being installed in highway traffic signal controller cabinets and railroad grade crossing equipment bungalows includes some ability to record event data. The data recorded, however, are not always either easily retrieved or of much use for effective analysis. Additionally, communication and data transmission between the highway and railroad systems is relatively limited.
This chapter summarizes the collection and analysis of information related to existing recording capabilities of devices installed within highway traffic signal controller cabinets and/or railroad grade crossing equipment bungalows. A brief description of a "market-available" event recording device is provided; no product endorsement is made or implied by its inclusion in this document. This chapter also documents current highway agency and railroad testing, inspection, and regulation practices pertaining to interconnected signal systems.
There are many different types of devices used in highway traffic signal controller cabinets that can record various types of events or information. These devices are manufactured according to several national standards for signal control assemblies, including NEMA TS-1, NEMA TS-2 Type 1, NEMA TS-2 Type 2, Type 170, Type 179, Type 2070, and ATC. Some agencies use a hybrid approach to highway traffic signal cabinet architecture and customize these standards to meet their unique individual requirements. Field examples of highway traffic signal control assemblies and data transfer set-ups are shown in Figure 1.
Table 1 summarizes the various highway traffic signal control device manufacturers, listed by device type. Based on the manufacturer listing, a sampling of events (or alarms) that can be recorded and stored as data in each highway traffic signal control cabinet device is presented in Table 2. Please note that the information presented in Table 1 and Table 2 is for highway traffic signal controller applications only. Additionally, the listing in Table 2 contains events (or alarms) related to highway traffic signal control that may be relevant in maintaining highway-rail grade crossing operation; not every event (or alarm) would be recorded, but could be investigated as second- or third-tier information if an incident did occur. Most in-cabinet event recording systems are focused on system malfunction monitoring of such anomalies as signal conflicts, field circuit failures, short interval occurrences, internal electrical levels out of range, and electrical noise. Traffic flow information can also be logged, as well as a variety of user-defined functions such as cabinet door open, keyboard data change, and system coordination status. The event recording capability varies depending on cabinet architecture. The exact number and type of events (or alarms) recorded also vary greatly depending on the type, model, and manufacturer of the device. Additionally, each device typically requires manufacturer-specific software to record and/or access the desired information.
Figure 1: Field Examples of Highway Traffic Signal Controller Assemblies and Data Transfer Set-ups
Table 1: Highway Signal Control Manufacturers Reviewed by Device Type
|Conflict Monitors / Malfunction Management Units||Econolite
Eberle Design Inc. (EDI)
Reno A & E
|Pre-emption Devices||EMTRAC Systems
Global Traffic Technologies (GTT)
|Vehicle Detection||Inductive Loops:
Eberle Design Inc. (EDI)
Global Traffic Technologies (GTT)
Reno A & E
Highway traffic signal control assemblies, when located in the vicinity of a highway-rail grade crossing, typically have a single point connection from the railroad grade detection/control system - one per approach. Upon receipt of a valid preempt call from the rail system, the highway traffic signal assembly will revert to a preempt state at the intersection. While standard highway traffic signal control assemblies have various levels of event/data recording capability, only those cabinets containing specialized recording units designed for such an application have the capability to log more detail than a preempt call being activated, the time the call was received, and the time the signal reverted back to normal operation. Events/data such as time of event signal display status, vehicle/pedestrian call status, preempt call reports, and sequence time duration is available from various devices; however, recording capabilities are typically contained in manufacturer-specific devices and not consolidated in a single device within a highway traffic signal control cabinet that is readily available for field review purposes. Information that is being recorded can be accessed on a device-by-device basis either through a front panel display on the device itself or via connection to a laptop computer containing the appropriate firmware designed to interrogate the device and retrieve such data. Typically, the laptop firmware required for data retrieval is manufacturer-specific to the device being interrogated.
Table 2: Sampling of Highway Signal Events (or Alarms) Recorded by Device Type
|DEVICE||EVENT (OR ALARM) RECORDED|
|Conflict Monitors /
Malfunction Management Units
|+24 VDC latch status
AC line - brownout
AC line - power down
AC line - short interrupt
AC line - voltage value
Configuration change - jumper selection
Configuration change - program card
Configuration change - switches
Control signal voltages
CVM latch status
Dual indication enable status
Entry to flash
Event monitoring trigger
Exit from flash
|Field check / dual indication switch status
Field signal voltages
Flash delay time
Graphical display of channel voltage levels
Minimum yellow change channel disable jumper status
Per channel voltage levels
Permissive channel jumper status
Port 1 fail
Signal sequence history ( 30 seconds prior to event)
Time line sequence log
Voltage limit faults
|Controllers||Alarm log fault
BIU frame error
Cabinet door open
Communication log fault
Conflict flash on/off
Controller power on/off
Coordination / free switch active
Coordination fault / cycle problem
Coordination fault / program problem
Cycle zero phase fault
Data change - keypad
Data change - remote
Local flash on / off
Manual control enable active
MMU field check fault
MMU minimum clear fault
MMU Port 1 failure
MMU red failure
No coordination - command free
No system command - back up operation
Preempt on / off
Priority on / off
Software clock adjust
System communications status
System off line - remote flash
System off line - voltage monitor
Time change - keypad
|Pre-emption Devices||Active channel call
Duration of event
End of event
Event green time
Final green phase
|Preempt call placed to controller
Priority (high / low)
Start time of event
|Vehicle Detection||Loop status|
In general, event/data recording capability within a railroad grade crossing equipment bungalow in the vicinity of a highway-rail grade crossing is dependent on a standalone unit rather than as an integral part of another installed device. The use of standalone event recorders allows railroads to deploy the same technology at different types of signal locations and in conjunction with equipment of varying age and manufacturer. It assists in the isolation of non-vital functions - such as event recording - from vital functions, allowing the railroads to have significant discretion as to what events/data are recorded. Many devices can be expanded, daisy chained, or networked to increase the number of inputs that railroad event recorders can monitor. Some newer systems incorporate elements that were formerly distinct units (e.g., grade crossing predictor, grade crossing controller, and event recorder); however, among existing crossing systems, these are the exception rather than the rule.
Table 3 summarizes by manufacturer the various railroad event recorders reviewed for this task. Table 4 presents a sampling of events (or alarms) that can be recorded. All of the devices listed Table 3 can record the identified events if the proper inputs are provided. Other events (e.g., temperature, train speed, gate up/down, etc.) require additional modules/sensors to provide the necessary inputs to the event recorder. The number and types of events actually recorded vary with each railroad's standard practice; however, most railroads do not record as many events as shown in the table. Please note that the information presented in Table 3 is for railroad event recording applications only.
Table 3: Railroad Event Recorder Manufacturers Reviewed by Device Type
VDL Microlok II (Data Logger)
VDL S7-300 (Data Logger)
|Micro Data Analyzer I
Micro Data Analyzer II
Universal Data Analyzer
Universal Recorder Module
|North American Signal|
Hawk Recorder (GETS)
Some devices employ more complex event recording functions and can monitor performance of the highway-rail grade crossing warning system. For example, if programmed correctly and provided with the proper inputs, an event recording device may be able to detect unsafe conditions such as gates not down within 5 seconds of a train occupying the island circuit or warning time of less than 20 seconds. Some devices can also assist in performing and recording monthly, quarterly, and yearly tests required by the FRA.
Device memory can typically store over 100,000 events, which can be retrieved through the device's graphic interface or by downloading to a laptop in the field using standard connections such as RS232 or USB. Data formats and communications capabilities vary by manufacturer. Devices may communicate by several methods, including dial-up modem, cellular modem, Ethernet modem, Base Communications Package (BCP), Mobile Communications Package (MCP) radio, VHF, UHF, and spread spectrum radio. The communication capabilities can be used to provide alarms to railroad control centers or to maintenance personnel in real time. Some devices also include GPS capabilities for location and time stamping.
Table 4: Sampling of Railroad Events (or Alarms) Recorded by Device Type
|DEVICE||EVENT (OR ALARM) RECORDED|
VDL Microlok II (Data Logger)
VDL S7-300 (Data Logger)
|AC and DC voltage levels
AC power on / off
Crossing warning equipment activation / deactivation
False crossing activation
Gate up / gate down
Interlocking logic operation
Low battery voltage
Stick circuit operation
Track occupancy - approach circuits and island circuits
Unauthorized facility entry
|Micro Data Analyzer I
Micro Data Analyzer II
Universal Data Analyzer
Universal Recorder Module
Hawk Recorder (GETS)
As shown in Tables 1 through 4, there are several prominent manufacturers of highway and railroad signal control devices. Likewise, there are a number of devices that can be assembled within a cabinet or bungalow architecture, each of which has its own capability to record various events. Depending on the type, model, and manufacturer of the device or the agency's standard practice, the number and type of events being recorded vary greatly. As such, one challenge is to determine which events can be recorded across different signal control architectures that will satisfy the two NTSB recommendations. A second challenge is to determine how to easily retrieve these events from the various devices being used. To date, the amount of data exchanged between highway and railroad signal control systems is limited; many times it is a single preemption call circuit. Much more data will need to be consolidated and supplied to the recording device, whether it is located in the highway traffic signal controller cabinet or railroad grade crossing equipment bungalow. Another significant challenge will be addressing the existing electrical isolation that exists between the two systems, as any data exchanged will require a common electrical reference. A proposed single recording device will have several technical challenges. These challenges will be addressed in subsequent sections pertaining to technical guidelines.
One currently available device that does support the recording of events in both highway traffic signal cabinets and railroad bungalows that may be of interest is "Interconnected Grade-Crossing Operations Recorder (IGOR)". This event recording device was recently developed through a partnership between Campbell Technology Corporation (CTC) and Reno A&E. IGOR units are installed in both the highway traffic signal controller cabinet and the railroad grade crossing equipment bungalow and can be integrated into various system architectures. The device records events such as traffic signal state, right-of-way transfer time, track clearance green time, and gate and flashing warning light status. The device also has the ability to record high-definition video, if desired. An informational brochure for IGOR is provided in Appendix A.
Highway agency and railroad personnel can be important sources of information when seeking to understand the technical capabilities of currently deployed event recording devices in highway and railroad signal control systems. Using the United States Department of Transportation (USDOT) FRA National Highway-Rail Grade Crossing Inventory database (3), the number of locations per State where interconnected highway-rail recording devices are currently deployed were identified. Additionally, consideration was given to the FRA's top 10 "worst" States for highway-rail grade crossing accidents/incidents on average during the time period 2006 through 2008.
From these sources, a prioritized list of 12 States was created to contact for further information. The 12 States are listed below and highlighted in Figure 2:
Figure 2: Priority States
State traffic engineers from each of the 12 identified States were contacted, as well as personnel at a number of Class I railroads and commuter rail/transit organizations. Table 5 summarizes the railroads contacted. The objective of these contacts was to gain further insight of the following:
An initial email was sent to the various contacts requesting that the recipient forward contact information for personnel directly related to highway-rail grade crossing operation and maintenance; only a limited number of responses were received. From State highway agencies, direct contact information for related personnel was received from California, Georgia, Minnesota, and New Jersey. From the railroads, responses were received from three Class I railroads and one commuter railroad. As a follow up to the initial email, direct phone calls were made in an attempt to solidify further contacts for future questioning; however, these efforts did not produce additional State highway agency or railroad responses.
Table 5: Railroads Initially Contacted
|Class I||Burlington Northern Santa Fe Railway (BNSF)
Canadian National (CN)
Canadian Pacific (CP)
|Kansas City Southern (KCS)
Norfolk Southern (NS)
Union Pacific (UP)
|Commuter Rail / Transit||Amtrak
Dallas Area Rapid Transit (DART)
Maryland Area Regional Commuter (MARC)
MTA - Long Island Railroad (LIRR)
MTA - Metro North
San Francisco Bay Area Rapid Transit (BART)
SCRRA - MetroLink
SFRTA - Tri-Rail
Sound Transit - Seattle
Southeastern Pennsylvania Transportation Authority (SEPTA)
Utah Transit Authority (UTA) - Salt Lake City
Virginia Rail Express (VRE)
A questionnaire was sent to the respondents with regard to existing recording device deployment practices as well as testing and inspection policies and practices. The questionnaire sent to the respective highway agencies and railroads is included as Appendix B. In addition to existing technical and policy information that is vital to developing practical guidelines for interconnected highway-rail recording devices, the questionnaire also sought to gain insight on the financial ramifications of such devices. This includes more than just the initial cost of the device, with consideration being given to associated costs such as installation, operation, service life, interfacing with existing infrastructure, maintenance (preventative and reactionary), and other indirect costs such as staff training relative to the device. With the limited number of responses from highway agency and railroad personnel, providing a comprehensive assessment of the financial impacts of such devices proved to be difficult.
The following summarizes the state-of-practice based on the questionnaire responses received from the various State highway agencies and railroads.
Until recently, highway traffic signal systems generally did not have recording devices that can be used to assist with preventive maintenance. The majority of States responded that, within the traffic signal controller cabinet, the controller and the malfunction management unit (MMU) can record events related to preemption calls and similar types of events. It was noted that in-cabinet devices store a predetermined amount of system activity before overwriting files. One State responded that they have event recorders at two crossings equipped with "health" monitors that report directly to the railroad. Responses also indicated that the railroads will typically install event recording devices within new bungalows. Other than the use of a supervisory circuit, no other information or data was reported as being exchanged between highway and railroad traffic signal control facilities in the field.
From the responses, two different design plans were indicated: two conductor, normally closed circuit activation and four conductor. With regard to the four conductor, the pairs reported were preempt relay, supervisory relay, gate down relay, and supervisory latch relay. One State noted that, while two conductor closed loop is acceptable, four conductor is normally used. Example block diagrams/wiring diagrams of "typical" installations depicting interconnected highway-rail signal control systems already in place are shown in Appendix C.
Battery back-up systems (BBS) are available to support critical highway traffic signal functions. One State responded that a few of their highway traffic signals are equipped with BBS, but not at all highway-rail grade crossings. Another State indicated that installing BBS is a design standard for all of their new signals with railroad preemption. Overall, the provision of BBS at new and upgraded highway traffic signal installations is becoming standard practice for several agencies. Railroad signal systems typically have their own BBS, which do not supply back up power to an adjacent highway traffic signal control system.
The majority of the responses indicated that highway-rail grade crossing facilities are not remotely monitored. One State did respond that many of their highway traffic signals at railroad crossings with preemption are structured with closed loop signal systems that have the capability of providing remote monitoring. These signals can be called up via telephone line, providing an agency with various levels of remote system monitoring and control capability. These types of systems can report back the number of railroad preemption calls and certain malfunctions.
At this time, responding highway agencies did not envision or anticipate future plans to modify how highway and railroad signal control systems are interconnected.
Highway agencies test the circuitry that interfaces the traffic and rail signal controllers. This is typically done at the initial turn-on of new highway-rail interconnected signal system installations. The majority of the responses indicated that no approved inspection or testing checklists were available. Instead, technicians use checklists developed by the local or regional highway agency. As an example, one State responded that a technician will place the highway traffic signal into flash mode by creating an open circuit and disconnect the highway-rail interconnect wire. Upon attempting to reset, the highway traffic signal should not exit flash mode. Another State indicated that, if possible, a train will be present for testing or the team will wait for the arrival of a train to observe correct operation. Most responses noted that representatives from the responsible railroad are not required to be present at the initial testing and turn-on, but their presence is requested. Typically, personnel from both the highway agency and the railroad are present.
Preventive maintenance and testing practices varied across the responses received. Intervals range from monthly to quarterly to bi-annually to annually. One State responded that they do not engage in such practices. Similar to initial turn-on, respondents indicated that there is typically no written procedure or checklist for these activities. One State did, however, supply documentation of their preventive maintenance and testing practice protocols. Another State indicated that they are in the process of developing a standardized inspection and reporting method. Maintenance activities as well as periodic inspections and testing are often recorded and filed for several years. Local or district highway operations offices typically initiate and lead the preventive maintenance and testing activities. Railroad personnel are typically not present during these activities unless requested by the local or district highway agency or if a problem is noted with rail equipment. However, railroads may be provided a copy of the work performed for their records.
Railroads generally have event recorders installed at the majority of highway-rail grade crossings. Depending on the railroad, every new or updated crossing in the last 5 to 10 years has an event recorder installed. Event recorders identified by respondents include:
For the most part, the recorders installed are standalone devices; however the SEAR IIi is integrated into the railroad signal controller.
Not all railroads record the exact same inputs and alarms at highway-rail grade crossings. Generally, power off, gate down, island presence, and dropping of the preemption circuit are recorded by all railroads at locations with a device installed. Some railroads record more information such as alarms when lights are not flashing; when the gate is all the way up, starting to go down, and all the way down; and when the train reaches the approach, each side of the island circuit, and when it clears the opposite approach. A railroad may choose not to record more inputs or alarms if it has older equipment installed that cannot store as much information or data as the newer equipment.
Event recorders are generally not used by railroads to conduct testing and inspection of the crossing and are not regularly downloaded as part of any inspection procedure; however, some railroads may occasionally check the log history for short warning times. Railroads typically allow event recorders to store data in memory until it begins overwriting rather than transmitting the information to a central location. If a report is needed for a claim or an incident, it is downloaded on site.
The coverage of crossings that are remotely monitored ranges from 5 to 40 percent, depending on the railroad. If an element of the crossing does not operate as it was set up or intended, an alarm is sent to a central office. This can be done a number of different ways: through radio, a cellular modem, phone line, or even a third party, which then calls the railroad.
Railroads typically have their own standard drawings for preemption circuit installation. These generally follow American Railway Engineering and Maintenance-of-Way Association (AREMA) standards for preemption circuits (at least functionally), but may differ slightly depending on the location or age of the crossing. Railroad acquisitions may inherit crossings with different preemption circuit layouts. Railroads are generally aware of new signal equipment capabilities that can pass additional information (other than the preemption request) between the railroad signal controller and the highway traffic signal controller; however, they are not availing themselves of it.
Example block diagrams/wiring diagrams of "typical" installations depicting interconnected highway-rail signal control systems already in place are shown in Appendix C. Example preemption circuits are not provided due to concerns with confidentiality.
For the initial inspection of newly installed or upgraded interconnected highway-rail grade crossings, railroads typically test the entire crossing following the Code of Federal Regulations (CFR), but do not have any special procedures that are required to be followed. The highway agencies are informed of the inspections by the railroads, but they often do not participate in the testing.
For the testing of highway traffic signal preemption, railroads follow the federal regulations, which require that preemption interconnections are tested once per month for proper operation. This test requires verification that the preemption circuit opens up when the crossing relay (XR) drops, but does not entail testing the actual preemption time provided at the highway traffic signal. The railroads' test procedures generally do not vary by State and do not contain any tests beyond what is required by the CFR.
Some States may require railroads to conduct a joint inspection of the highway traffic signal preemption with the highway agency. Railroads would like to verify that the highway traffic signal controller received the preemption indication as well as visually observe at what time the queue actually clears from the crossing. Typically, only the railroad is required to sign off on the inspection. If a joint inspection is conducted, railroads require that participating highway agency personnel are properly trained for safe access and working within railroad right-of-way.
Railroads have also expressed scheduling concerns, as maintainers currently have difficulty meeting the existing requirements. At present, railroads would not generally use a device that can perform a self-test of preemption to replace the required monthly inspections. The railroads generally suggested that such devices would be used daily or weekly and probably at night, but only as an additional aid to the human tests each month. Once these devices are industry- and FRA-approved, they could be a huge time saver for the railroads.
This section addresses inspection and testing of highway and railroad signal systems as prescribed in various literature sources.
Currently, there is no national highway traffic signal inspection policy that mandates what is to be inspected, how the inspection is to be conducted, and when the inspection should take place. Highway traffic signal system testing and inspection processes are typically developed by State or local highway agencies. The 1989 edition of the ITE Traffic Signal Installation and Maintenance Manual (4) states, "Maintenance problems can often be traced to inadequate inspection during signal equipment installation...A major contributing factor is often the lack of comprehensive inspection guidelines, including a final acceptance "punch list" to ensure a thorough, systematic inspection by the field inspector."
The International Municipal Signal Association (IMSA) has created a Traffic Signal Inspection Certification Program to educate and certify field technicians in the inspection of highway traffic signal installations. Inspection topics include traffic signal displays and supports, underground and overhead equipment, vehicular and pedestrian detection systems, controller assemblies, safety requirements, electrical grounding and bonding, and final acceptance and turn-on. The knowledge is intended to ensure that specified construction practices are properly followed during signal installation, resulting in correct operation.
The IMSA course and the 2010 ITE Traffic Signal Maintenance Handbook (5) provide guidance for inspection and testing of highway traffic signals through construction to acceptance; however, no guidance is provided for similar activities post-acceptance. In the 1989 edition of the ITE Traffic Signal Installation and Maintenance Manual, the chapter on risk management provides a section specific to periodic inspections and reviews. This section states, "Review of court cases indicates that, in general, a 6-month interval for routine inspection is considered a reasonable exercise of due care. Thus, conduct of the routine preventative maintenance program as outlined in Chapter 4 should meet the basic requirements for routine inspection." Chapter 4 states, "...preventative maintenance should be performed on detector equipment every 3 months; on signal controller cabinets, signals, and related equipment at 6- or 12-month intervals; on controller equipment generally on an annual basis." The preventative maintenance checklist with recommended intervals is included in Appendix D. Again, it is noteworthy that this information does not appear in the more recent 2010 publication.
Title 49 Part 234 Subpart D of the Code of Federal Regulations (49 CFR Part 234) (6) details all of the maintenance standards and requirements for inspecting and testing highway-rail grade crossing signal systems. Each railroad must comply with maintenance and testing procedures outlined in the CFR and is required to document these tests and provide them to the FRA. In addition to the test reports, railroads are required to document all incidents that occur within the railroad right-of-way and file these reports with the FRA. Railroad organizations that do not comply with 49 CFR are subject to fines imposed by the FRA.
Inspection and testing of highway-rail grade crossings are required at monthly, quarterly, and annual intervals. Most Class I railroads, Amtrak, and major commuter railroads have developed documented procedures to satisfy these requirements, some of which go beyond the 49 CFR requirements. Appendix E presents further information regarding the monthly, quarterly, and yearly testing requirements defined under various rules of 49 CFR, particularly warning system operation, warning time, and highway signal preemption.
With regard to event recording devices, 49 CFR does not contain any laws mandating the maintenance or inspection of devices used to monitor highway-rail grade crossings. The railroads are under no regulatory requirement to install event recorders as part of their Automatic Highway Warning System (AHWS). However, for locations with an event recording device installed as part of the AHWS, the lack of maintenance and inspection regulation results in widely varying practices.
Currently in the United States, according to the FRA grade crossing inventory, there are a total of 215,820 at-grade railroad crossings. Of these, highway traffic signal preemption is used at 4,954 (approximately 2%). As stated in Section 8C.09 of the Manual on Uniform Traffic Control Devices (MUTCD) (7), "If a highway-rail grade crossing is equipped with a flashing-light signal system and is located within 200 feet of an intersection or midblock location controlled by a traffic control signal, the traffic control signal should be provided with preemption in accordance with Section 4D.27. Coordination with the flashing-light signal system, queue detection, or other alternatives should be considered for traffic control signals located farther than 200 feet from the highway-rail grade crossing. Factors to be considered should include traffic volumes, highway vehicle mix, highway vehicle and train approach speeds, frequency of trains, and queue lengths. The highway agency or authority with jurisdiction and the regulatory agency with statutory authority, if applicable, should jointly determine the preemption operation and timing of traffic control signals interconnected with highway-rail grade crossings adjacent to signalized highway intersections."
According to 49 CFR, highway-rail grade crossing warning systems must provide a minimum of 20 seconds of warning. If preemption is necessary, the preemption time is added to the minimum warning time to determine the track detection point of the approaching train. Also, under Section 8C.09 of the MUTCD, "If preemption is provided, the normal sequence of traffic control signal indications shall be preempted upon the approach of trains to avoid entrapment of highway vehicles on the highway-rail grade crossing."
At highway-rail grade crossings with preemption, the FRA regulates the railroad portion of the system; however, the FRA has no regulatory means to assure that the highway portion of the system is working as desired.
The CFR regulates the railroads and requires them to conduct regular inspections of their equipment. The highway authorities are under no federal inspection regulations and are not required to inspect their equipment. The railroads generally feel that, until the highway authorities are required to regularly test their equipment, a joint inspection would be difficult to conduct.
A major concern for the railroads is liability. The highway agency does all of the traffic signal design, calculates the necessary warning time to clear the intersection, and then informs the railroad how much warning time is needed. The railroad then provides the necessary time; however, the railroad personnel are not familiar with the highway traffic signal equipment or the process of calculating the warning time. The overall opinion of the railroads is that it is not necessary or practical to have railroad personnel looking into whether or not the highway traffic signal preemption is working beyond testing that the circuit is being dropped coming out of the railroad equipment box. The railroads maintain that they should not be responsible for inspecting anything on the highway side of the preemption and are not comfortable signing off on whether or not a highway traffic signal is working properly.