COLLECTION AND MAINTENANCE OF DATA

The FHWA requires each State to develop and implement a HSIP that consists of three components: planning, implementation, and evaluation. The process for improving safety and operations at highway-railroad grade crossings consists of the same three components and may be considered part of a State's HSIP.

FHWA policy and procedures for an HSIP are contained in the Federal-Aid Policy Guide (FAPG) Title 23–Code of Federal Regulations (and Non-Regulatory Supplements)93 The purpose of an HSIP is to reduce fatalities and serious injuries on all public roads, including the development of a data-driven Strategic Highway Safety Plan (SHSP), Railway-Highway Crossings Program, and program of highway safety improvement projects. Types of safety data includes, but are not limited to, crash, roadway characteristics, and traffic data on all public roads. For railway-highway crossings, safety data also includes the characteristics of highway and train traffic, licensing, and vehicle data.

USDOT Grade Crossing Inventory

Under FRA regulations in subpart F to 49 CFR Part 234, railroads are required to report highway-rail and pathway crossings to the National Crossing Inventory.94 The USDOT National Highway-Rail Crossing Inventory was developed in the early 1970s through the cooperative efforts of FHWA, the FRA, the AAR, individual States, and individual railroads. Originally this was a voluntary effort by the various stakeholders. A PDF file of the USDOT Crossing Inventory Form can be downloaded from: https://www.fra.dot.gov/eLib/Details/L16197. The railroads assign each crossing a unique DOT Crossing Inventory Number consisting of six numeric characters and an alphabetic character. To obtain new DOT Crossing Inventory Numbers, railroads should email RequestDOTGXNumber@dot.gov and provide the following:

• Name of person requesting the number(s)
• Title of person requesting the number(s)
• Email address of the person request the number(s)
• Railroad name
• Railroad mailing address
• Number of DOT crossing numbers(s) requested

The FRA is the custodian for the Crossing Inventory database. The data for the Inventory is provided by the railroad and States. The railroads and States can find the Guide for Preparing USDOT Crossing Inventory Forms (Guide). The Guide explains what information is required for each box of the Inventory Form. The Guide also includes information on what fields of the Inventory are the responsibility of the railroads and what fields are the responsibility of the States.

According to the Guide, a railroad must update the Crossing Inventory record for each open at-grade crossing at least once every three years; however certain changes require more frequent updates:

• New crossings must be reported to the Inventory within 6 months of becoming operational
• Closure or sale of a crossing must be reported to the Inventory within 3 months
• Change in crossing surface must be reported to the Inventory within 3 months
• Changes in warning devices must be reported to the Inventory within 3 months

To maintain consistency with accident history and other data, once an Inventory Number is assigned to a crossing it should not be assigned to another location.

Highway-Rail Grade Crossing Collision Data

Information on highway-rail grade crossing collisions is also needed to assess safety and operations. Data on collisions involving trains are essential in identifying crossings with safety problems. In addition, data on collisions not involving trains but occurring at or near a crossing are useful. For example, non-train-involved collisions may indicate a deficiency in stopping sight distance such that a vehicle suddenly stops at a crossing, causing the following vehicle to hit the leading vehicle in the rear.

Collision data is available from several sources, including State and local police and FRA. In addition, the NHTSA and FHWA maintain some information on crossing collisions. The FRA's Office of Safety Analysis has a website (also known as Safetydata) where their updated data is uploaded. This can be accessed at https://safetydata.fra.dot.gov.

Information regarding accidents, reporting, and investigations can be accessed at https://www.fra.dot.gov/Page/P0037.

The FRA Guide for Preparing Accident/Incident Reports can be found online at https://www.fra.dot.gov/eLib/details/L18093#p1_z5_gD_kpreparing%20accident. A PDF file of the Accident Report Form for Federal Railroad Administration can be downloaded from: https://safetydata.fra.dot.gov/officeofsafety/publicsite/Newregulation.aspx?doc=F6180_54_Expires06302020.pdf. NHTSA maintains a database on all fatal highway traffic collisions, including those occurring at highway-rail grade crossings. The FARS database can be accessed at https://www.nhtsa.gov/research-data/fatality-analysis-reporting-system-fars (see Figure C-1).

The FMCSA maintains data on highway collisions involving motor carriers. An accident is "an occurrence involving a commercial motor vehicle operating on a highway engaged in interstate or intrastate commerce which results in (i) a fatality; (ii) bodily injury to a person who, as a result of the injury, immediately receives medical treatment away from the scene of the accident; or, (iii) one or more motor vehicles incurring disabling damage as a result of the accident, requiring the motor vehicle(s) to be transported away from the scene by a tow truck or other motor vehicle" (49 CFR 390.5).(95)

In the past, FMCSA required motor carriers to report crashes directly to the agency. This is no longer the case. This information is now forwarded by States; however, motor carriers must maintain accident registers for three years after the date of each accident occurring on or after April 29, 2003 (49 CFR 390.15).

Collisions involving the transport of hazardous materials are reported to PHMSA. The PHSMA develops regulatory programs to help ensure the safe and secure movement of hazardous materials. The PHSMA also enforces the Federal Motor Carrier Safety Regulations which can be found in 49 CFR 350-399.

Significant transportation accidents are investigated by the NTSB. The NTSB issues a report for each accident investigated. The report presents the circumstances of the accident, the data collected, and the analysis of the data as well as conclusions, which are identified as "findings" of NTSB. In addition, NTSB issues specific recommendations to various parties for improvement of safety conditions.

Figure C-1. Rail Equipment Accident/Incident Report Form

Source: FRA, Office of Safety (website accessed) https://safetydata.fra.dot.gov/officeofsafety/publicsite/ReportingRequirement.aspx.

HAZARD INDICES AND ACCIDENT PREDICTION FORMULAE

A systematic method for identifying crossings that have the most need for safety and/or operational improvements is essential to ensure that federal and State funds for highway-railroad grade crossing improvement projects are spent at the locations that are considered to be most in need of improvement. Considerations for prioritizing locations for improvement include the following:

• The potential reduction in the number and/or severity of collisions
• The cost of the projects and the resources available
• The relative hazard of public highway-rail grade crossings based on a hazard index formula
• Collision history of a particular crossing location
• On-site inspections of public crossings
• The potential danger to large numbers of people at public crossings used on a regular basis by passenger trains, school buses, transit buses, pedestrians, bicyclists, or by trains and/ or motor vehicles carrying hazardous materials
• Other criteria as appropriate in each State

To support the prioritization process, various hazard indices and collision prediction formulae have been developed to assist with ranking the hazard potential of highway-rail grade crossings. A hazard index ranks crossings in relative terms (the higher the calculated index, the more hazardous the crossing), whereas the collision prediction formulae are intended to compute the actual collision occurrence frequency at the crossing. These are commonly used to identify crossings to be investigated in the field. A 2017 review of State DOT hazard ranking practices found that 39 out of 50 States (78 percent) utilized some type of hazard ranking index, collision prediction formula, or other systematic method for prioritization.(96) This section discusses the application of hazard index techniques and crash prediction formula techniques for highway-railroad grade crossing hazard ranking. Procedures for conducting the on-site inspection are discussed in the next section.

It should be noted that hazard indices or crash prediction formulas are not the exclusive method used by State DOTs and other agencies to identify hazardous highway-railroad grade crossings. Crossings may also be selected for field investigation because of requests or complaints from the public. State district offices, local governmental agencies, other State agencies, and railroads may also request that a crossing be investigated for improvement. A change in highway or railroad operations over a crossing may justify the consideration of that crossing for improvement. For example, a new residential or commercial development may increase the volume of highway traffic over a crossing such that its hazard index would increase. Other crossings may be selected for a field investigation because they are utilized by buses, passenger trains, and vehicles transporting hazardous materials. Some States incorporate these considerations into a hazard index, thus providing an objective means of assessing the potential danger to large numbers of people. Finally, professional judgment on the part of the highway-rail intersection safety specialist in determining the appropriateness of a particular warning device project at a particular crossing location should also be considered in the process.

Hazard Index

The hazard index approach to prioritization of grade crossing locations requires the analyst to calculate a ranking metric or value that will provide insight into the hazard level of a particular crossing relative to other crossing locations. A commonly used index is the New Hampshire Hazard Index ranking methodology. Historically, the New Hampshire Hazard Index was the most common hazard ranking model used by State DOTs. A 2017 review of State DOT grade crossing hazard ranking practices found that at least seven States were utilizing the New Hampshire Hazard Index, or a State-specific variation thereof, for prioritization activities.(96) The New Hampshire Hazard Index is the most basic form of the hazard index model type consisting of the exposure index (cross product of the AADT and train volume) with a "protection factor" adjustment for the type of warning device provided at the crossing. The New Hampshire Hazard Index formula is as follows:

• HI = (V) * (T) * (PF), where:
• HI = Calculated Hazard Index Value
• V = Highway Traffic Volume at Crossing (AADT)
• T = Train Movements per Day at Crossing
• PF = Protection Factor based on Warning Device Type

The original New Hampshire Hazard Index formula utilized protection factors of 0.1 for automatic gates, 0.6 for flashing lights, and 1.0 for signs only. Some States have revised these protection factors to include more refined levels of protection available at a crossing. For example, the Michigan DOT utilizes the New Hampshire Hazard Index with 13 different values of protection factors based on the presence of additional warning device features.(97) The primary advantage of the hazard index approach is that it is easily understood. An increase in either highway traffic volume or train traffic volume increases the risk of a crash at a crossing location; that risk is lower if more sophisticated protective devices are present at that location. The primary disadvantage of the hazard index approach is that the hazard index value is calculated relative to other crossings; consequently, the hazard index value for a single crossing without reference to other crossings has limited usefulness for prioritization.

Crash Prediction Model

The crash prediction model approach to prioritization of grade crossing locations utilizes a mathematical formula to predict the expected annual crash frequency at a crossing location; this value is used as the ranking metric for prioritization purposes. A crash prediction model is intended to estimate, in absolute terms, the likelihood of a collision occurring over a given period of time based on the given conditions at the crossing. Some crash prediction models also allow for the severity of crashes to be predicted. The structure of the crash prediction models includes all the characteristics or factors that are thought to significantly influence the risk of a crash at a grade crossing. A crash prediction model can also be used to either rank crossings or identify potential high-accident locations for further review. Additionally, the model output can be combined with economic data on crash costs to support a comprehensive economic analysis of proposed grade crossing improvement projects.

A 2017 review of State DOT grade crossing hazard ranking practices found that at approximately half of the States utilized a crash prediction formula of some type for prioritization activities. Crash prediction formulas currently in use by State DOTs include the USDOT Accident Prediction Model, the NCHRP 50 Accident Prediction Model, the Peabody-Dimmick formula. Additionally, some States have developed crash prediction models based on State-specific crash trends and experiences. Among the crash prediction models currently in use, the USDOT Accident Prediction Model is the most prevalent, with at least 19 States (38 percent) reporting the use of this model for prioritization activities. Additional details of the USDOT Accident Prediction Model are presented in this section; details of other, less commonly-used crash prediction models, are available elsewhere.(96)

USDOT Accident Prediction Model

The USDOT Accident Prediction Model is an accident prediction model that was developed in the mid-1970s to support a comprehensive grade crossing project selection process known as the Rail-Highway Crossing Resource Allocation Procedure⁽⁹⁸⁾ The most up-to-date version of the USDOT Accident Prediction Model is described in detail in the FRA's GradeDec.net Crossing Evaluation Tool Reference Manual, which was published in 2014.⁽⁹⁹⁾ The USDOT crash prediction model is a multi-stage calculation that combines three independent calculations to produce a crash prediction value. The basic formula provides an initial hazard ranking based on a crossing's characteristics, like other formulae such as the Peabody-Dimmick formula and the New Hampshire Index. The second calculation utilizes the actual collision history at a crossing over a determined number of years to produce a collision prediction value. This procedure assumes that future collisions per year at a crossing will be the same as the average historical collision rate over the time period used in the calculation. The third equation adds a normalizing constant, which is adjusted periodically to keep the procedure matched with current collision trends. If desired, the analyst can also predict the annual frequency of crashes by crash severity (fatality, injury, or property damage only).

The basic steps to utilize the USDOT Accident Prediction Model are as follows:

• Step 1: Gather Required Input Data
• Step 2: Generate Preliminary Crash Frequency Estimate
• Step 3: Adjustment for Crash History
• Step 4: Normalizing Constant Adjustment for Crash Trends
• Step 5: Estimate of Crash Severity (Optional)

The specific requirements for each step listed above are described in the following sections. Specific formula information and numerical parameters are obtained directly from the FRA GradeDec.net manual.⁽⁹⁹⁾ The FRA has provided a web-based tool, known as the Web Accident Prediction System, where highway-rail intersection safety specialists may view current estimates of the predicted annual crash frequency for any public highway-rail intersection in the national inventory database.

ENGINEERING STUDY

Federal requirements (23 U.S.C. 130(d)) dictate that each State develop a crossing program based on the following:

• The potential reduction in collisions or collision severities
• The project costs and available resources
• The relative hazard of each crossing based on a hazard index formula
• An onsite inspection of each candidate crossing

An engineering study is the comprehensive analysis and evaluation of available pertinent information, and the application of appropriate principles, provisions, and practices. MUTCD Part 1A.13 requires that an engineering study shall be performed by an engineer, or by an individual working under the supervision of an engineer, through the application of procedures and criteria established by the engineer. Based on a review of these conditions, an assessment of existing and potential hazards can be made. If safety deficiencies are identified, countermeasures can be recommended.

An engineering study should be conducted of highway-rail crossings that have been selected from the priority list. The purpose of this study is to accomplish the following:

• Review the crossing and its environment
• Identify the nature of any problems
• Recommend alternative improvements

Diagnostic Team Study Method

The Diagnostic Team Study Method is the procedure adopted in FHWA's Highway Safety Engineering Study Procedural Guide and adopted in concept by several States.(100) This survey procedure utilizes experienced individuals from several sources. The procedure involves the Diagnostic Team's evaluation of the crossing as to its deficiencies and consensus as to the recommended improvements.

The primary factors to consider when determining stakeholders to be a part of the Diagnostic Team are that the team is interdisciplinary, and representative of all groups having responsibility for the safe operation of crossings. This enables each of the vital factors relating to the operational and physical characteristics of the crossing to be identified properly. Individual team members are selected based on their specific expertise and experience. The overall structure of the team is built upon the following three desired areas of responsibility:

• Local responsibility
• Administrative responsibility
• Advisory capability

For the purpose of the Diagnostic Team, the operational characteristics of crossings can be classified into the following three areas:

Traffic Operations

This area includes both vehicular and train traffic operation. The responsibilities of highway traffic engineers and railroad operating personnel chosen for team membership include, among other criteria, specific knowledge of highway and railroad safety, types of vehicles and trains, and their volumes and speeds.

Traffic Control Devices

Highway maintenance engineers, signal control engineers, and railroad signal engineers provide the best source for expertise in this area. Responsibilities of these team members include knowledge of active traffic control systems, interconnection with adjacent signalized highway intersections, traffic control devices for vehicle operations in general and at crossings, and crossing signs and pavement markings.

Administration

Many issues relating to crossing safety also involve the apportionment of administrative and financial responsibility. This should be reflected in the membership of the Diagnostic Team. The primary responsibility of these members is to advise the team of specific policy and administrative rules applicable to the modification of crossing traffic control devices.

To ensure appropriate representation on the Diagnostic Team, it is suggested that the team be comprised of at least a traffic engineer with safety experience as well as a railroad signal engineer. Following are other disciplines that might be represented on the Diagnostic Team:

• Railroad administrative official
• Highway administrative official
• Human factors engineer
• Law enforcement officer
• Regulatory agency official
• Railroad operating official
• Local government agencies
• Regional transportation planning organization
• Pedestrian/bicycle coordinator
• Emergency services representative
• Commercial motor carrier
• Stakeholders and special interest groups

The Diagnostic Team should study all available data (including as-built plans and/or proposed improvement plans that may impact the location) and inspect the crossing and its surroundings with the objective of determining the conditions that affect safety and traffic operations. In conducting the study, a questionnaire is recommended to provide a structured account of the crossing characteristics and their effect on safety. Some States are now using automated diagnostic review forms to facilitate the collection, storage, and analysis of crossing data. Figure C-2 shows a sample questionnaire, which can be altered to fit individual agency needs. The questionnaire shown in Figure C-2 is divided into the following four sections:

• Distant approach and advance warning
• Immediate highway approach
• Crossing proper
• Summary and analysis

Important considerations when studying traffic flow and operations at a highway-rail grade crossing are traffic volumes (daily and peak hour); speeds; the mix of vehicle types; intersecting volumes and turning movements at intersections near the crossing; the capacity of the road; delays; and the formation of any traffic queues. These should be reviewed in light of current conditions and how they might be affected by changes at the crossing.

Key concerns are routing and access for emergency vehicles and the use of the crossing by special vehicles such as low clearance vehicles, buses, and trucks transporting hazardous materials.

Locational Data:

Street Name:

City:

Railroad:

Crossing Number

VEHICLE DATA: No. of Approach Lanes

Approach Speed Limit:

AADT

Approach Curvature: ______________________________ Approach Gradient:__________________________________

TRAIN DATA: No. of Tracks:__________________________________ Train Speed Limit:__________________________________

Trains Per Day:__________________________________

Track Gradients:__________________________________

SECTION I–Distance Approach and Advance Warning

1. Is advance warning of railroad crossing available? If so, what devices are used?

---

2. Do advance warning devices alert drivers to the presence of the crossing and allow time to react to approaching train traffic?

---

3. Do approach grades, roadway curvature, or obstructions limit the view of advance warning devices?_____ If so, how?

---

4. Are advance warning devices readable under night, rainy, snowy, or foggy conditions?

---

SECTION II–Immediate Highway Approach

1. What maximum safe approach speed will existing sight distance support?

---

2. Is that speed equal to or above the speed limit on that part of the highway?

---

3. If not, what has been done, or reasonably could be done, to bring this to the driver's attention?

---

4. What restrictive obstructions to sight distance might be removed?

---

5. Do approach grades or roadway curvature restrict the driver's view of the crossing?

---

6. Are railroad crossing signals or other active warning devices operating properly and visible to adequately warn drivers of approaching trains?

---

SECTION III–Crossing Proper

1. From a vehicle stopped at the crossing, is the sight distance down the track to an approaching train adequate for the driver to cross the tracks safely?

---

2. Are nearby intersection traffic signals or other control device affecting the crossing operation? If so, how?

---

3. Is the stopping area at the crossing adequately marked?

---

4. Do vehicles required by law to stop at all crossings present a hazard at the crossing? _____ Why?

---

5. Do conditions at the crossing contribute to, or are they conducive to, a vehicle stalling at or on the crossing?

---

6. Are nearby signs, crossing signals, etc. adequately protected to minimize hazards to approaching traffic?

---

7. Is the crossing surface satisfactory? _____ If not, how and why?

---

8. Is surface of highway approaches satisfactory? _____ If not, why?

---

SECTION IV–Summary and Analysis

1. List major attributes of the crossing which may contribute to safety:

---

2. List features which reduce crossing safety:

---

3. Possible methods for improving safety at the crossing (including closure, if practicable):

---

4. Overall evaluation of crossing:

---

5. Other comments:

---

Figure C-2. Sample Questionnaire for Diagnostic Team Evaluation

To help the Diagnostic Team identify viewpoints of reference for the field evaluation, traffic cones can be placed on the approaches, as shown in Figure C-3.

Figure C-3. Study Positions for Diagnostic Team

Crossing Approach Zone

Cone A is placed at the point where the driver first obtains information that there is a crossing ahead. This distance is also the beginning of the approach zone. Usually, this information comes from the advance warning sign, the pavement markings, or the crossing itself. The distance from the crossing is based on the decision sight distance (refer to bottom row of Table C-1), which is the distance required for a driver to detect a crossing and to formulate actions needed to avoid colliding with trains. In calculating sight distances, a level approach is assumed. If this is not the case, an allowance should be made for the effects of positive or negative approach grades.

Table C-1. Sight Distances for Combinations of Highway Vehicle and Train Speeds - Distance Along Railroad Crossing from dT (ft)

Train Speed (MPH)	Case B Departure from Stop	Case A Moving Vehicle
		Vehicle Speed (MPH)
–	0	10	20	34	40	50	60	70	80
Distance Along Railroad Crossing from d, (ft)
10	255	155	110	102	102	106	112	119	127
20	509	310	220	203	205	213	225	239	254
30	794	465	331	305	307	319	337	358	381
40	1,019	619	441	407	409	426	450	478	508
50	1,273	774	551	509	511	532	562	597	635
60	1,528	929	661	610	614	639	675	717	763
70	1,783	1,084	771	712	716	745	787	836	890
80	2,037	1,239	882	814	818	852	899	956	1,017
90	2,292	1,394	992	915	920	958	1,012	1,075	1,144
Distance Along Highway from Crossing, d,, (ft)
–	–	69	135	220	324	447	589	751	931

Source: American Association of State Highway and Transportation Officials (AASHTO): A Policy on Geometric Design of Highways and Streets, 7th Edition, Washington, DC, 2018.

Safe Stopping Point

Cone B is placed at the point where the approaching driver has adequate corner sight distance to see an approaching train so that a safe stop can be made if necessary. This point is located at the end of the approach zone and the beginning of the non-recovery zone. Distances to point B are based on the design vehicle speed and maximum authorized train speed (refer to "Case A– Moving Vehicle" in Table C-1).

Stop Line

Cone C is placed at the stop line, which is assumed to be 15 feet from the near rail of the crossing, or 8 feet from the gate if one is present.

The questions in Section I of the questionnaire (refer to Figure C-2) are concerned with the following:

• Driver awareness of the crossing
• Visibility of the crossing
• Effectiveness of advance warning signs and signals
• Geometric features of the highway

When responding to questions in this section, the crossing should be observed from the beginning of the approach zone, at traffic cone A.

The questions in Section II of the questionnaire (refer to Figure C-2) are concerned with whether the driver has sufficient information to detect an approaching train and make correct decisions about crossing safely. Observations for responding to questions in this section should be made from cone B. Factors considered by these questions include the following:

• Driver awareness of approaching trains
• Driver dependence on crossing signals
• Obstruction of view of train's approach
• Roadway geometrics diverting driver attention
• Potential location of standing railroad cars
• Possibility of removal of sight obstructions
• Availability of information for stop or go decision by the driver

The questions in Section III of the questionnaire (refer to Figure C-2) apply to observations adjacent to the crossing, at cone C. Of concern, especially when the driver must stop, is the ability to see down the tracks for approaching trains. Intersecting streets and driveways should also be observed to determine whether intersecting traffic could affect the operation of highway vehicles over the crossing. Questions in this section relate to the following:

• Sight distance down the tracks
• Pavement markings
• Conditions conducive to vehicles becoming stalled or stopped on the crossing
• Operation of vehicles required by law to stop at the crossing
• Signs and signals as fixed object hazards
• Opportunity for evasive action by the driver

In Section IV of the questionnaire (see Figure C-2), the Diagnostic Team is given the opportunity to do the following:

• List major features that contribute to safety
• List features that reduce crossing safety
• Suggest methods for improving safety at the crossing
• Give an overall evaluation of the crossing
• Provide comments and suggestions relative to the questionnaire

In addition to completing the questionnaire, team members should take photographs of the crossing from both the highway and the railroad approaches.

Current and projected vehicle and train operation data should be obtained from the team members. Information on the use of the crossing by buses, school buses, trucks transporting hazardous materials, and passenger trains should be provided. The evaluation of the crossing should include a thorough evaluation of collision frequency, collision types, and collision circumstances. Both train-vehicle collisions and vehicle-vehicle collisions should be examined.

Team members should drive each approach several times to become familiar with all conditions that exist, at or near, the crossing. All traffic control devices (signs, signals, markings, and train detection circuits) should be examined as part of this evaluation. If the crossing is equipped with signals, the railroad signal engineer should activate them so that their alignment and light intensity may be observed.

The MUTCD should be a principal reference for this evaluation. Also, A User's Guide to Positive Guidance provides information for conducting evaluations of traffic control devices.(101)

After the questionnaire has been completed, the team is reassembled to discuss it. Each member should summarize his or her observations pertaining to safety and operations at the crossing. Possible improvements to the crossing may include the following:

• Closing of crossing–available alternate routes for highway traffic
• Site improvements–removal of obstructions in the sight triangle, highway realignment, improved cross section, drainage, or illumination
• Crossing surfaces–rehabilitation of the highway structure, the track structure, or both; installation of drainage and subgrade filter fabric; adjustments to highway approaches; and removal of retired tracks from the crossing
• Traffic control devices–installation of passive or active control devices and improvement of train detection equipment

The results and recommendations of the Diagnostic Team should be documented. Recommendations should be presented promptly to programming and implementation authorities. Current practice is to use a team in order to ensure all stakeholder perspectives are included.

Sight Distance Computation

Available sight distances help determine the safe speed at which a vehicle can approach and clear a crossing. Refer to the AASHTO "Green Book" for additional information.(87) The following three sight distances should be considered (refer to Figures C-4 and C-5):

• Distance ahead to the crossing–Approach stopping sight distance
• Distance to and along the tracks on which a train might be approaching the crossing from either direction–Corner sight distance
• Sight distance along the tracks in either direction from a vehicle stopped at the crossing– Clearing sight distance

Figure C-4. Sight Distance for Moving Vehicle

Source: American Association of State Highway and Transportation Officials (AASHTO): A Policy on Geometric Design of Highways and Streets, 7th Edition, (Figure 9-77), Washington DC, 2018.

The formula for computing safe stopping distance for vehicles approaching a crossing is set forth in the following formula (refer to Figure C-4):

where:

• A = constant = 1.47
• B = constant = 1.075
• d H = sight distance measured along the highway from the nearest rail to the driver of a vehicle, which allows the vehicle to be safely stopped without encroachment of the crossing area, feet
• Vv = velocity of the vehicle, mph
• t = perception-reaction time, seconds, assumed to be 2.5 seconds
• a = driver deceleration, assumed to be 11.2 feet per second2
• D = distance from the stop line or front of vehicle to the near rail, assumed to be 15 feet
• de = distance from the driver to the front of the vehicle, assumed to be 8 feet

The minimum safe sight distances, dH, along the highway for selected vehicle speeds are shown in the bottom line of Table C-1. As noted, these distances were calculated for level approaches to 90-degree crossings and should be increased for less favorable conditions.

The second sight distance utilizes a so-called "sight triangle" in the quadrants on the vehicle approach side of the track. This triangle is formed by:

• The distance (dH) of the vehicle driver from the track
• The distance (dT) of the train from the crossing

This sight triangle is depicted in Figure C-4. The distance along the along the railroad (dT) is determined by the vehicle speed and maximum timetable train speed and is set forth in the following formula:

where:

• dT = sight distance along the railroad tracks to permit the vehicle to cross and be clear of the crossing upon arrival of the train
• VT = velocity of the train, mph
• Vv = velocity of the vehicle, mph
• A = constant = 1.47
• B = constant = 1.075
• t = perception-reaction time, seconds, assumed to be 2.5 seconds
• a = driver deceleration, assumed to be 11.2 feet per second
• D = distance from the stop line or front of vehicle to the near rail, assumed to be 15 feet
• L = length of vehicle, assumed to be 65 feet
• W = distance between outer rails (for a single track, this value is 5 feet)

Clearing Sight Distance

In the case of a vehicle stopped at a crossing, the driver needs to see both ways along the track to determine whether a train is approaching and to estimate its speed. The driver needs to have a sight distance along the tracks that will permit sufficient time to accelerate and clear the crossing prior to the arrival of a train, even though the train might come into view as the vehicle is beginning its departure process.

Figure C-5 illustrates the maneuver. These sight distances, for a range of train speeds, are given in the column for a vehicle speed of zero in Table C-1. These values are obtained from the following formula:

where:

• dT = sight distance along the railroad tracks to permit the vehicle to cross and be clear of the crossing upon arrival of the train
• VT = velocity of the train, mph
• VG = maximum speed of vehicle in selected starting gear; assumed to be 8.8 feet per second
• a1 = acceleration of vehicle in starting gear, assumed to be 1.47 feet per second2
• D = distance from the stop line or front of vehicle to the near rail, assumed to be 15 feet
• L = length of vehicle, assumed to be 65 feet (see Table C-2 for further clarification)
• W = distance between outer rails (for a single track, this value is 5 feet)
• d = distance the vehicle travels while accelerating to maximum speed in first gear, assumed to be 26.4 feet
• J = Perception-reaction time (3 seconds)

Adjustments for longer vehicle lengths, slower acceleration capabilities, multiple tracks, skewed crossings, and other than flat highway grades are necessary. The formulas in this section may be used with proper adjustments to the appropriate dimensional values. It would be desirable that sight distances permit operation at the legal approach speed for highways, however, this is often impractical.

Figure C-5. Sight Distance for Stopped Vehicle

Source: American Association of State Highway and Transportation Officials (AASHTO): A Policy on Geometric Design of Highways and Streets, 7th Edition, (Figure 9-68), Washington DC, 2018.

Pedestrian Sight Distance Triangle

Evaluation of clearing sight distance at a pedestrian crossing should consider the pedestrian walking speed, the maximum authorized speed of trains at the crossing, as well as a decision/ reaction distance and buffer zone (refer to Figure C-6).

Table C-2 provides computed values for both pedestrians as well as typical highway vehicles. The pedestrian sight distance, which is shown in the right-hand column, is based upon the following quantities: walking speed of 3.5 feet per second, 10 feet for decision/reaction distance (about 2.8 seconds), 15-foot track centers, a dynamic envelope of 11 feet, and a 6-foot buffer zone. In this example, the pedestrian will traverse the 42-foot distance in 12 seconds. The required sight distance is then computed by considering the distance the train will traverse in 12 seconds based upon the approach speed. At crossings where this distance is not available, active control devices should be considered. It should be noted that crossing users cannot be expected to reliably judge the precise approach speed of a train, so practitioners should consider that the required distances represent an absolute minimum.

Figure C-6. Pedestrian Sight Distance Triangle (Double Track Crossing)

Source: Institute of Transportation Engineers.

Table C-2. Clearing Sight Distances (in Feet)

Train Speeda	Cara	Single-unit Trucka	Busa	WB-50 Semitrucka	65-foot Double Trucka	Pedestrianb
10	105	185	200	225	240	180
20	205	365	400	450	485	355
25	255	455	500	560	605	440
30	310	550	600	675	725	530
40	410	730	795	895	965	705
50	515	910	995	1,120	1,205	880
60	615	1,095	1,195	1,345	1,445	1,060
70	715	1,275	1,395	1,570	1,680	1,235
80	820	1,460	1,590	1,790	1,925	1,410
90	920	1,640	1,790	2,015	2,165	1,585

a A single track, 90-degree, level crossing.

b Walking 3.5 feet per second across two sets of tracks 15 feet apart, with a 2-second reaction time to reach a decision point 10 feet before the center of the first track, and clearing 10 feet beyond the centerline of the second track. Two tracks may be more common in commuter station areas where pedestrians are found.

Source: Guidance on Traffic Control Devices at Highway-Rail Grade Crossings. Washington, DC: Federal Highway Administration, Highway/Rail Grade Crossing Technical Working Group, November 2002.

Corridor Approach

The procedures for evaluating highway-rail grade crossings are generally based upon the physical and operational characteristics of individual crossings. A typical crossing safety program consists of several individual crossing projects. Funding for crossing safety is approved based on the requirements of these individual projects. Therefore, crossing evaluation, programming, and construction follow traditional highway project implementation procedures.

The corridor approach may be applied to an urban area, city, or community. In this case, all public crossings within the jurisdiction of a public agency are evaluated and programmed for improvements. The desired outcome is a combination of engineering improvements and closures such that both safety and operations are highly improved.

A corridor approach developed for crossings in a specified community or political subdivision provides for a comprehensive analysis of highway traffic operations. Thus, unnecessary crossings can be closed, and improvements can be made at other crossings. This approach enhances the acceptability of crossing closures by local officials and citizens.

Initially, all crossings in the system, both public and private, should be identified and classified by jurisdictional responsibility (for example, city, county, and State for public crossings; parties to the agreement for private crossings). This also includes crossings with train speeds from 80-110 mph. Information should be gathered on highway traffic patterns, train operations, emergency access needs, land uses, and growth trends. Inventory records for the crossings should be updated to reflect current operational and physical characteristics. A Diagnostic Team consisting of representatives from all public agencies having jurisdiction over the identified crossings and the railroads operating over the crossings should make an on-site assessment of each crossing (as described in the previous section). The Diagnostic Team's recommendations should consider, among other things, crossing closure, installation of traffic control devices, upgrading existing traffic control devices, crossing elimination by grade separation, surface improvements, and improvements in train detection circuits. For railroad crossing locations interconnected to the traffic signaling system, appropriate timing should be re-evaluated to determine whether simultaneous or advanced preemption is suitable. The use of pre-signals and queue-cutter signals should also be explored, where warranted, to assist the preemption phasing to safely clear vehicles off the track prior to the activation of the railroad flasher lights and gates.

Federal, State, and local crossing funding programs should be reviewed to identify the eligibility of each crossing improvement for public funding. Other funding sources including railroads, urban renewal funds, land development funds, and other public or private funding sources should also be explored.

There are several advantages of the corridor approach. A group of crossings may be improved more efficiently through the procurement of materials and equipment in quantity, thus reducing product procurement and transportation costs. Usually, only one agreement between the State, local jurisdiction, and railroad is necessary for all the improvements. Train detection circuits may be designed as a part of the total railroad signal system rather than custom designed for each individual crossing. Electronic components, relay houses, and signal transmission equipment may be more efficiently utilized. Labor costs may be significantly reduced and travel time of construction crews may be reduced when projects are near each other.

If a crossing consolidation is contemplated, the effects on traffic circulation and the impact on the operation of adjacent intersections should be considered. Frequently, the consolidation of crossings also leads to the consolidation of traffic on other facilities and may permit the construction of a traffic signal at a nearby intersection or other improvements that could not be justified otherwise. In light of these and other potential impacts, communication with first responders on any changes with crossings should be considered a priority.

Railroads benefit from the application of the systems approach in several ways. Train speeds may be increased due to safety improvements at crossings. Maintenance costs may be reduced if enough crossings are closed. Other improvements may enhance the efficiency of rail operations.

Safety improvements are an obvious benefit to the public. Other benefits include reduced vehicular delays and better access for emergency vehicles.

The traffic study should also consider the impacts of crossing operations on the community. Considerations include frequency and length of train operations, pedestrian and bicycle access, and the need for crossings to provide adequate access to schools and services.

Standard data collection procedures can be found in several sources, including the Highway Safety Engineering Studies Procedural Guide or the Manual of Transportation Engineering Studies from the Institute of Transportation Engineers.(100,102)