Prevention and Mitigation of Bridge and Tunnel Strikes (2025)
Chapter: 6 BrTS Data Analysis
CHAPTER 6
BrTS Data Analysis
According to the previous definitions, there are two kinds of bridge strikes: 1) on-bridge strikes and 2) under-bridge strikes. On-bridge strikes occur either 1a) when a vehicle strikes the bridge railing/parapet, or 1b) when an OHV strikes the overhead bridge structure part. However, according to the crash data collected from the 23 states so far, these two groups of on-bridge vehicle strikes are difficult to differentiate. Similarly, for under-bridge strikes, they happen either 2a) when a vehicle hits a bridge support (such as a pier or a parapet) or an abutment, or 2b) when an OHV strikes the overhead bridge structure, such as a bridge deck or any form of deck protection.
Tunnel strikes can also be divided into two types: OHV tunnel strikes and in-tunnel crashes. OHV tunnel strikes are similar to OHV strikes in that both occur when a vehicle is too large to fit under the tunnel ceiling. In-tunnel crashes occur when a vehicle veers off the right-of-way and strikes a tunnel wall or retaining wall (as it is indicated in some state crash datasets) or a barrier within the tunnel. While bridge strikes are relatively simple to query from a crash dataset due to the existence of unique attributes denoting them and their type, tunnel strikes are more challenging. This is due to the fact that most states record tunnel strikes under the very common “Other Fixed Object” struck object attribute. Some states such as Nevada, Texas, and Washington have made it simpler to query their datasets for tunnel strikes by using unique attributes to indicate them or by having a dedicated column indicating whether the crash could be a tunnel strike. Washington and Texas have a custom attribute for hit objects that denotes tunnels. On the other hand, Nevada provides a distinct column indicating possible tunnel strikes.
BrTS are categorized by type for each state in Table 9. For all states, on-bridge OHV strikes and other on-bridge vehicle strikes (e.g., railing, parapet) cannot be distinguished. Tunnel strikes can be queried by specific data field and its attribute values for three states: Nevada, Texas, and Washington. In Texas, however, attributes cover multiple types of BrTS, including hitting top of underpass or tunnel, hit pier or support at underpass, tunnel or overhead sign bridge. The property damage variable may be used to further separate the various types; but at its current form, this data field is filled with noisy statements and is blank for half of the entries. For the rest of the states, tunnel crashes are either grouped with retaining wall strikes or labeled as “Other Fixed Object”. Colorado and Virginia, as an extreme example, lumped all BrTS strikes under one attribute. Wyoming provided their crash dataset which included only “Bridge Overhead Structure” strikes. The absence of uniformity in the crash data attributes for BrTS creates a challenge to estimate the extent of the safety impact and strengthen the knowledge of the root causes of vehicle collisions occurred to bridges and tunnels.
Table 10 shows a summary of crash statistics for different types of BrTS for the 23 states that provided crash data. On-bridge strikes, under-bridge strikes with overhead structure, and under-bridge strikes with pier or support account for 57.8%, 21.5% and 20.7% of strikes, respectively. As the most common bridge strike, on-bridge strikes are 1.37 times more common than under-bridge strikes, including both OHV strikes and under bridge strikes with substructures. Single-vehicle crashes are predominant across all three types of bridge strikes. The dominance is the highest in under-bridge strikes by OHVs where the ratio between single vehicle (SV) and multi-vehicle (MV) is 9.13 to one; under-bridge strikes with substructures have a ratio of 7.18 to one; lastly, on-bridge strikes have a ratio of 6.62 to one. The primary first harmful event in a MV is the collision with another vehicle in transport, or one or more the vehicles engaged in striking with
the bridge. It is arguable that bridge characteristics such as cross-sectional design, traffic volume and mix can be attributed to bridge hits; therefore, both SV and MV crashes are considered.
The number and quality of tunnel strikes by motor vehicles vary considerably across the states, making it difficult to generate accurate tunnel crash statistics. Washington is an exception, as it has a dedicated attribute for tunnel strikes. For the remaining states, tunnel strikes can be queried by the general attribute under which the tunnel crashes are placed. Then, vehicles that strike within 1,500 feet to a tunnel are labeled as tunnel strikes. A further review of the crash narrative is preferred in order to verify that all events are true tunnel strikes. Several states such as Arkansas, Idaho and Iowa reported no tunnel hits during the data collection period. Overall, the number of tunnel strikes make up a small percentage of all BrTSs.
Table 11 shows the overall situation of the statistics by different injury severity (i.e., in KABCO scale) for all types of bridge-related crashes. The analysis is limited to bridge-related crashes because results from the spatial join for potential tunnel crashes (i.e., fixed object collision) are too unreliable to generate the injury severity statistics. As can be seen, the number of bridge strikes varies widely from state to state due to factors such as the number of bridges, type of bridges, traffic volume (especially truck traffic), and crash reporting criteria. The distribution of fatal and injury crashes is relatively consistent across the states. On average, the percentage of fatal crashes is 1.7% of total BrTSs with a standard deviation of 0.8%. Fatal crashes range from zero in Oregon to 3.2% in Alaska. The average BrTS fatal percentage among these states is more than three times the national average, according to the NHTSA six-year average crash statistics. The average bridge strike injury percentage is 26.7% with a standard deviation of 14.4%, which is slightly lower than the six-year national average injury percentage of 29%. Among the states, the injury rate ranges from 14.4% in Connecticut to 43.9% in Oregon.
Table 9. BrTS Attributes Used by Each State
| States | BrTS Hit Categories | 1) On-bridge strikes (e.g., truss, parapet, railing) | 2) Under-bridge strikes with overhead structure (e.g., girder) | 3) Under-bridge strikes with pier or support (e.g., bent, support, pier, abutment) | 4) Other fixed object strikes (wall, building, tunnel, etc.) |
|---|---|---|---|---|---|
| Alaska | Bridge rail (includes parapet) | Bridge overhead structure | Bridge pier or support | Other fixed object | |
| Arkansas | Collision with bridge rail | Collision with bridge overhead structure | Collision with bridge pier or support | Collision with other fixed object | |
| Colorado | All bridge crashes are lumped together as bridge rail | N/A | |||
| Connecticut | Bridge rail | Bridge overhead structure | Bridge pier or support | Other fixed object (wall, building, tunnel, etc.) | |
| Florida | Bridge rail | Bridge overhead structure | Bridge pier or support | Other fixed object (wall, building, tunnel, etc.) | |
| Idaho | Bridge rail | Overpass | Bridge/pier/abutment | Other fixed object | |
| Illinois | Bridge end, Bridge rail | Bridge underside | Bridge support | Other fixed object | |
| Iowa | Bridge/bridge rail parapet | Bridge overhead structure | Bridge pier or support | NA | |
| Maine | Bridge rail | Bridge overhead structure | Bridge pier or support | Other fixed object (wall, building, tunnel, etc.) | |
| Michigan | Bridge rail | Bridge overhead structure | Bridge pier/support | Other fixed object | |
| Minnesota | Bridge rail | Bridge overhead structure | Bridge pier or support | Other fixed object | |
| Mississippi | Collision with bridge rail | Collision with bridge overhead structure | Collision with bridge pier or support | Collision with other fixed object (wall, building, tunnel, etc.) | |
| Nevada | Bridge rail | Bridge overhead structure | Bridge pier or support | Other fixed objects (building, tunnel, etc.)/inclusion of | |
| States | BrTS Hit Categories | 1) On-bridge strikes (e.g., truss, parapet, railing) | 2) Under-bridge strikes with overhead structure (e.g., girder) | 3) Under-bridge strikes with pier or support (e.g., bent, support, pier, abutment) | 4) Other fixed object strikes (wall, building, tunnel, etc.) |
|---|---|---|---|---|---|
| custom column used to label whether a crash is possibly a tunnel crash | |||||
| North Carolina | Bridge rail end, bridge rail face | Overhead part underpass | Pier in median of underpass pier on shoulder of underpass | Other fixed object | |
| Oregon | Bridge railing or parapet (on bridge or approach) | Bridge girder (horizontal bridge structure overhead) | Bridge pillar or column Bridge abutment (included “approach end” thru 2013) | Retaining wall or tunnel wall | |
| South Carolina | Bridge Parapet End, Bridge Rail | Bridge Overhead Structure | Bridge Pier Abutment | Other(Wall, Bldg, Tunnel, Etc.) | |
| Tennessee | Bridge/Parapet End, Bridge Rail | Bridge/Overhead Structure | Bridge/Pier Abutment | Other Fixed Object | |
| Texas | Hit end of bridge (abutment or rail end), hit side of bridge (bridge rail) | Hit top of underpass or tunnel, hit pier or support at underpass, tunnel or overhead sign bridge | |||
| Utah | Bridge Rail | Bridge Overhead Structure | Bridge Pier or Support | Other Fixed Object | |
| Virginia | Tunnel, Bridge, Underpass, Culvert, etc. Other Fixed Object | ||||
| Washington | Bridge Rail – Face, Bridge Rail – Leading End, Bridge Rail – Through, Over, or Under | Underside of Bridge | Bridge Abutment, Bridge Column, Pier or Pillar | Retaining Wall (concrete, rock, brick, etc.), Tunnel Wall / Barrier within Tunnel | |
| Wisconsin | BRPAR – Bridge Parapet End BRRAIL – Bridge Rail | BRIDGE – Bridge Overhead Structure | BRPIER – Bridge/Pier/Abut | OTH FX – Other Fixed Object | |
| Wyoming | NA | Bridge Overhead Structure | NA | NA | |
Table 10. Prototype of the BrTS Data Clearinghouse flat file.
| State Crash Records | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Field Name | BrTS ID | State | Date | Time | Latitude | Longitude | On Road | At Road | … |
| Format | CHARa(50)b | CHAR(2) | DATE | TIME | NUM(10,8)c | NUM(10,8) | CHAR(50) | CHAR(50) | … |
| Description | ID in data clearinghouse | State postal abbreviation | Date of crash YYYY/MM/DD | Time of crash | Decimal degrees | Decimal degrees | Name of road on which crash occurred | Name of intersecting road to identify location | … |
| 1001 | WI | 2018/11/09 | 8:45 | 43.87680426 | −91.1832326 | THIRD | WALNUT | … | |
| 1002 | WI | 2020/10/02 | 13:20 | 44.08444452 | −87.7236331 | US 29 | SR 1619 | … | |
| 1003 | NV | 2013/03/06 | 7:50 | 40.06118260 | −118.6534580 | PEACE | GLENNWOOD | … | |
| 1004 | NV | 2013/05/25 | 21:10 | 40.80916510 | −115.8246880 | SUTTON | ARLINGTON | … | |
| 1005 | MA | 2019/02/04 | 17:05 | 42.59224383 | −71.2805723 | NC 226 | POTEAT | … | |
| 1006 | MA | 2019/02/12 | 9:02 | 41.94660778 | −71.2755011 | SALISBURY | OLD CHARLOTTE | … | |
| NBI/NTI | ||||||||
|---|---|---|---|---|---|---|---|---|
| Field Name | BrTS ID | Structure Number | Structure Material | Structure Type | Minimum Vertical Clearance | Year Built | Detour Length | … |
| Format | CHAR(50) | CHAR(50) | CHAR(50) | CHAR(50) | NUM(3,2) | NUM(4,0) | NUM(3,0) | … |
| Description | ID in data clearinghouse | Structure number/bridge identification number | Structure material | Type of structure design | Minimum vertical clearance (over-bridge roadway) or minimum vertical underclearance (under-bridge roadway) in meters | Year the bridge was built | Kilometers | … |
| 1001 | B32005400000000 | Steel continuous | Stringer/multibeam or girder | 4.84 | 1967 | 1 | … | |
| 1002 | B36006500000000 | Prestressed concrete continuous | Stringer/multibeam or girder | 4.65 | 1979 | 24 | … | |
| 1003 | B1040W | Concrete | Culvert | — | 1965 | 1 | … | |
| 1004 | I900W | Prestressed concrete | Box beam or girders – multiple | 5.00 | 1976 | 1 | … | |
| 1005 | B120062BBMUNNBI | Concrete | Arch – deck | — | 1950 | 2 | … | |
| 1006 | A160203YYDOT634 | Steel | Stringer/multibeam or girder | 5.70 | 1962 | 3 | … | |
a CHAR indicates a data type storing characters in a fixed-length field.
b Numbers in parentheses specify data length. A single number means no decimal portion.
c Two numbers in parentheses also specify data length; the first is the number of integer digits, and the second is for decimal digits.
Table 11. Crash Statistics by State for Injury Severity of Bridge-Related Crashes6
| State | Year | Fatal | Injury | Property Damage Only (PDO) | Unknown | Total | ||
|---|---|---|---|---|---|---|---|---|
| Alaska | 2017 – 2020 | 2 | 3.23% | 16 | 25.81% | 39 | 5 | 62 |
| Arkansas | 2017 – 2021 | 65 | 2.88% | 792 | 35.12% | 1,398 | 0 | 2,255 |
| Colorado | 2016 – 2020 | 15 | 2.83% | 148 | 27.92% | 367 | 0 | 530 |
| Connecticut | 2015 – 2022 | 23 | 1.17% | 282 | 14.40% | 1,654 | 0 | 1,959 |
| Florida | 2016 – 2020 | 61 | 1.94% | 1,038 | 32.93% | 2,053 | 0 | 3,152 |
| Idaho | 2017 – 2021 | 10 | 2.82% | 132 | 37.18% | 213 | 0 | 355 |
| Illinois | 2017 – 2021 | 74 | 1.36% | 1,162 | 21.29% | 4,223 | 0 | 5,459 |
| Iowa | 2017 – 2021 | 26 | 1.44% | 538 | 29.74% | 1,245 | 0 | 1,809 |
| Maine | 2017 – 2021 | 0 | 0.00% | 118 | 25.65% | 342 | 0 | 460 |
| Michigan | 2017 – 2022 | 45 | 1.19% | 887 | 23.52% | 2,840 | 0 | 3,772 |
| Minnesota | 2017 – 2021 | 16 | 1.13% | 361 | 25.49% | 1,039 | 0 | 1,416 |
| Mississippi | 2019 – 2021 | 26 | 1.64% | 474 | 29.96% | 1,082 | 0 | 1,582 |
| Nevada | 2016 – 2020 | 2 | 1.92% | 43 | 41.35% | 59 | 0 | 104 |
| North Carolina | 2017 – 2021 | 54 | 2.54% | 636 | 29.87% | 1,334 | 105 | 2,129 |
| Oregon | 2015 – 2019 | 21 | 2.49% | 371 | 43.91% | 453 | 0 | 845 |
| South Carolina | 2017 – 2021 | 38 | 2.36% | 525 | 32.57% | 1,049 | 0 | 1,612 |
| Tennessee | 2017 – 2021 | 77 | 2.23% | 1,011 | 29.31% | 2,243 | 118 | 3,449 |
| Texas | 2017 – 2021 | Cannot Differentiate Bridge/Tunnel Crashes* | ||||||
| Utah | 2017 – 2021 | 4 | 1.96% | 66 | 32.35% | 134 | 0 | 204 |
| Virginia | 2017 – 2021 | Cannot Differentiate Bridge/Tunnel Crashes* | ||||||
| Washington | 2017 – 2021 | 35 | 0.95% | 854 | 23.11% | 2,664 | 142 | 3,695 |
| Wisconsin | 2017 – 2021 | 26 | 1.13% | 544 | 23.73% | 1,722 | 0 | 2,292 |
| National Total7 | 2015 – 2020 | 205,018 | 0.54% | 11,123,665 | 29.03% | 26,982,781 | 0 | 38,311,463 |
*: Cannot separate tunnel strikes from bridge strikes; and therefore, bridge strikes by injury severity are not generated.
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6 The discrepancies may exist between Tables 8 and 9. For example, the total number of bridge strikes for North Carolina is 2109 in Table 8, but this number is 2129 in Table 9. The reason is that the full sequence of events is not available (only the first four) in some states’ crash database. So, generating crash count by collision type might lose a few records. Same situation happens to Arkansas, Oregon, South Carolina, and Maine.
7 NHTSA, Crash Facts: 2015-2020.
