Washington State I-5 Bridge Collapse

This is a synopsis from the NTSB's report and does not include the Board's rationale for the conclusions, probable cause, and safety recommendations. NTSB staff is currently making final revisions to the report from which the attached conclusions and safety recommendations have been extracted. The final report and pertinent safety recommendation letters will be distributed to recommendation recipients as soon as possible. The attached information is subject to further review and editing.

EXECUTIVE SUMMARY

On Thursday, May 23, 2013, about 7:05 p.m. Pacific daylight time, a 2010 Kenworth truck-tractor in combination with a 1997 Aspen flatbed semitrailer hauling an oversize load (referred to here as “the oversize combination vehicle”) was traveling south on Interstate 5 (I-5) near Mount Vernon, Washington. The oversize combination vehicle had a permit for the route of travel and was being led by a pilot/escort vehicle, a 1997 Dodge Ram pickup truck. As the oversize combination vehicle traveled across the I-5 bridge above the Skagit River, the oversize load struck the bridge, damaging its structure. The oversize combination vehicle continued to travel across the bridge and came to a stop on I-5 south of the bridge.

As a result of contact damage to the bridge’s truss structure, span 8 of the 12-span bridge collapsed into the Skagit River. Two passenger vehicles, a southbound 2010 Dodge Ram pickup truck towing a Jayco travel-trailer and a northbound 2013 Subaru XV Crosstrek, fell into the river. Two other vehicles were damaged during the event: a 2000 Kenworth truck-tractor in combination with a 1996 refrigerated semitrailer in the southbound passing lane made contact with the oversize combination vehicle, and a southbound 1995 BMW 525i following the oversize combination vehicle received undercarriage damage. Eight vehicle occupants were involved in the bridge span collapse; three received minor injuries and five were uninjured.

CONCLUSIONS

  1. None of the following were factors in the crash: (1) driver fatigue, (2) driver health, (3) driver impairment, (4) federal commercial vehicle oversight by the United States or Canada, (5) weather conditions, or (6) mechanical condition of the oversize combination vehicle.
  2. The bridge span collapse sequence began when the oversize load struck sway brace 4 in span 8 on the west truss, causing deformation of the adjacent vertical member (L4-U4), which pulled the attached upper chord member (U3–U5) downward, causing a buckling failure in that upper chord member at node U4.
  3. Because the Skagit River Bridge was a non-load-path-redundant structure, buckling of the upper chord on the west truss resulted in the failure of the east truss and the collapse of span 8.
  4. The height of the casing shed load on the oversize combination vehicle was greater than the vertical clearance at the right edgeline of the southbound travel lanes on the Skagit River Bridge.
  5. Mullen Trucking LP did not adequately consider the vertical clearance or the reduced width of the travel lanes on the Skagit River Bridge when planning the route of the oversize combination vehicle.
  6. By not communicating any information about the narrow lane widths on the bridge or the reduced overhead clearance in the right lane of travel to the oversize combination vehicle driver before they reached the Skagit River Bridge, the pilot/escort vehicle driver failed to fulfill the duties of a pilot/escort driver.
  7. The pilot/escort vehicle driver was distracted by her hands-free cell phone conversation, which reduced her attention to her escort duties.
  8. Even if the pilot/escort vehicle driver had communicated the reduced overhead clearance in the right lane to the oversize combination vehicle driver while she was on the bridge, she was not maintaining an adequate lead distance, and the oversize combination vehicle was following too closely, to provide sufficient time for the oversize combination vehicle to stop before reaching the low-clearance hazard.
  9. Had the driver of the oversize combination vehicle been able to move safely from the right to the left lane before reaching the bridge, it is likely that his vehicle would not have struck the bridge.
  10. A permitting process that enables a carrier to self-issue a permit via an online procedure, without engaging the state in any technical review of the requested permit, does not motivate carriers to conduct route surveys before transporting oversize loads.
  11. Given the inability of a height pole to represent a three-dimensional load across a lane of travel, conducting an effective route survey calls for using a mechanism that more accurately represents the dimensions of the intended load.
  12. Had Mullen Trucking LP studied and fully understood the clearance data on the bridge list, it might have identified the different vertical clearances for the lanes of travel on the Skagit River Bridge and defined a lane-specific route of travel for the oversize combination vehicle that would have enabled it to avoid striking the bridge.
  13. The protection of bridge infrastructure is too vital a state concern to leave the responsibility for assessing the risk associated with the transportation of oversize loads entirely with the motor carrier.
  14. Neither the state nor the motor carrier seemed aware of the necessity to take any precautions due to the lane width reduction on the Skagit River Bridge.
  15. The lack of standardization of training for pilot/escort vehicle drivers among the states and the failure of the majority of states to require certification or training of such drivers leaves some pilot/escort vehicle drivers poorly prepared to carry out their duties.
  16. Pilot/escort vehicle drivers would benefit from better and more consistent guidance about the setting and placement of height poles, with a focus on placement in relation to known obstacles.
  17. Pilot/escort vehicle drivers should be clearly directed to research the bridge clearance data for their route provided by state departments of transportation before undertaking any escort assignment.
  18. Due to their special safety responsibilities, pilot/escort vehicle drivers should not engage in distracting activities and should be prohibited from using portable electronic devices (other than those designed to support the pilot/escort vehicle driving task) for nonemergency purposes, except to communicate safety-related information to the escorted vehicle.
  19. The Pilot Car Escort Best Practices Guidelines and related training materials would be improved by a thorough technical review to ensure that the information they contain reflects the most up-to-date recommended practices.
  20. The circumstances of this bridge strike demonstrate that drivers conducting oversize load operations need special knowledge to plan safe routes, coordinate effectively with pilot/escort vehicles, and control and position oversize loads.
  21. States are missing opportunities to reduce bridge strikes by not having formal processes to communicate bridge strike data from the department of transportation offices responsible for bridges and structures to the department of transportation offices responsible for permitting operations, and by not using such data to track the effectiveness of bridge strike countermeasures.
  22. Adding roadway clearance data to navigation systems on commercial motor vehicles would be a direct and efficient method of providing drivers with safe route information for oversize loads.
  23. State and local jurisdictions and the commercial motor vehicle industry would benefit from additional and improved guidance about the risks of high load strikes and the countermeasures that could help prevent them.
  24. Low-clearance signs in advance of and on bridges and tunnels provide valuable warnings to drivers of vehicles carrying overheight loads to help them avoid striking overhead obstructions.
  25. The Manual on Uniform Traffic Control Devices for Streets and Highways has not been kept consistent with the revised American Association of State Highway and Transportation Officials policy concerning bridge clearances.
  26. Drivers of overheight vehicles would benefit from having a warning sign that indicates the proper lane of travel for their vehicles when traveling underneath an arched structure.

PROBABLE CAUSE

The National Transportation Safety Board determines that the probable cause of the Interstate 5 Skagit River Bridge span collapse was a strike to the bridge structure by an oversize combination vehicle that failed to travel in a lane with adequate overhead clearance due to deficiencies in the interdependent system of safeguards for oversize load movements. These deficiencies included (1) insufficient route planning by Mullen Trucking LP and the oversize combination vehicle driver; (2) failure of the certified pilot/escort vehicle driver to perform required duties and to communicate potential hazards, due in part to distraction caused by cell phone use; and (3) inadequate evaluation of oversize load permit requests and no provision of low-clearance warning signs in advance of the bridge by the Washington State Department of Transportation.

RECOMMENDATIONS

To the Federal Highway Administration:

  1. Develop a best practices guide that the states can use to prevent bridge strikes by overheight vehicles. At a minimum, the guide should include (1) a framework for collecting bridge strike data and for ensuring communication of these data among the state agencies responsible for conducting bridge inspections and those responsible for issuing oversize load permits, to support the development of countermeasures; (2) practices for using the data to develop operational changes; (3) methods for evaluating bridge strike countermeasures; and (4) a review of countermeasures that have proven effective in reducing the number of bridge strikes by overheight vehicles in the states and in other countries. (H-14-XX)
  2. Work with the American Association of State Highway and Transportation Officials to amend the Manual on Uniform Traffic Control Devices for Streets and Highways, in accordance with A Policy on Geometric Design of Highways and Streets and the Load and Resistance Factor Design Bridge Design Specifications, to include a requirement for low-clearance signage for highway structures that cross over a roadway. The requirement should provide a uniform minimum clearance height between the roadway and the bottom of the structure which, if not met, necessitates the installation of low-clearance signage. (H-14-XX)
  3. Notify the state departments of transportation of the circumstances of the collapse of the Skagit River Bridge span, and create a timetable for those states that need to change their low-clearance signage requirements to conform to the uniform minimum clearance requirement proposed in Safety Recommendation [2]. (H-14-XX)
  4. Include in the Manual on Uniform Traffic Control Devices for Streets and Highways a requirement for signage indicating the proper lane of travel for overheight vehicles traveling under an arched structure. (H-14-XX)

To the Federal Highway Administration, the Specialized Carriers & Rigging Association, and the Commercial Vehicle Safety Alliance:

  1. Work together to revise the Pilot Car Escort Best Practices Guidelines and related training materials to ensure that they contain updated recommended practices for pilot/escort vehicle operations, and disseminate the revised documents to groups that provide pilot/escort vehicle driver training. (H-14-XX)

To the 50 states, the District of Columbia, and the Commonwealth of Puerto Rico:

  1. Ban the nonemergency use by pilot/escort vehicle drivers of portable electronic devices (other than those designed to support the pilot/escort vehicle driving task), except to communicate hazard-related information to the escorted vehicle. (H-14-XX)

To the Washington State Department of Transportation:

  1. Revise your bridge list to provide lane-specific clearance data for all structures. (H-14-XX)
  2. Revise your permit process for commercial vehicle services to include a state evaluation of the route’s overhead clearances and lane widths with respect to submitted load dimensions. (H-14-XX)
  3. Require both lead and trailing pilot/escort vehicles for any segment of a permitted route in which the permitted vehicle’s dimensions are as wide as, or wider than, the travel lane. (H-14-XX)
  4. Provide a geospatial application for route-specific bridge clearance data as a component of the effort you have begun to improve the permit process for oversize loads. (H-14-XX)

To the American Association of State Highway and Transportation Officials:

  1. Develop a method for replicating all the dimensions of an oversize load for use in pilot/escort vehicle operations. (H-14-XX)
  2. Work with the Federal Highway Administration to amend the Manual on Uniform Traffic Control Devices for Streets and Highways, in accordance with A Policy on Geometric Design of Highways and Streets and the Load and Resistance Factor Design Bridge Design Specifications, to include a requirement for low-clearance signage for highway structures that cross over a roadway. The requirement should provide a uniform minimum clearance height between the roadway and the bottom of the structure which, if not met, necessitates the installation of low‑clearance signage. (H-14-XX)

To the American Association of Motor Vehicle Administrators:

  1. Distribute to your members, and encourage the use of, the method developed by the American Association of State Highway and Transportation Officials in response to Safety Recommendation [11] for replicating all the dimensions of an oversize load for use in pilot/escort vehicle operations. (H-14-XX)
  2. Institute, with the assistance of the American Association of State Highway and Transportation Officials and the Commercial Vehicle Safety Alliance, a model training and certification process that includes reciprocity of certification in all 50 states, the District of Columbia, and the Commonwealth of Puerto Rico for drivers of pilot/escort vehicles, based on the Pilot Car Escort Best Practices Guidelines. (H-14-XX)
  3. Develop, with assistance from the Commercial Vehicle Safety Alliance and the Specialized Carriers & Rigging Association, training and testing materials that address the challenges and unique operating characteristics of the transportation of oversize loads, and distribute the developed information to state licensing agencies to institute a commercial driver’s license endorsement for oversize loads. (H-14-XX)

To the American Association of State Highway and Transportation Officials and the Commercial Vehicle Safety Alliance:

  1. Assist the American Association of Motor Vehicle Administrators in instituting a model training and certification process that includes reciprocity of certification in all 50 states, the District of Columbia, and the Commonwealth of Puerto Rico for drivers of pilot/escort vehicles, based on the Pilot Car Escort Best Practices Guidelines. (H-14-XX)

To the Commercial Vehicle Safety Alliance and the Specialized Carriers & Rigging Association:

  1. Assist the American Association of Motor Vehicle Administrators in developing training and testing materials that address the challenges and unique operating characteristics of the transportation of oversize loads, and distribute the developed information to state licensing agencies to institute a commercial driver's license endorsement for oversize loads. (H-14-XX)

To Nokia HERE, Google Inc., and Rand McNally:

  1. Develop reliable clearance data for highway structures, and incorporate that data into commercial vehicle navigation systems to help improve the routing and permitting of oversize loads. (H-14-XX)