The National Transportation Safety Board’s (NTSB) preliminary report on a fatal traffic incident that occurred earlier this month in Illinois doesn’t contain analysis or name a probable cause. It does, however, include a step-by-step breakdown of the complicated event which shows how varying speeds, sizes and positions of the vehicles involved affected the outcome.

The collision – or collisions – occurred on March 1 in Elmhurst, Illinois amid partially stopped traffic on Interstate 290. The roadway in this area has three travel lanes and paved shoulders in both directions of travel. A concrete barrier separates the eastbound and westbound lanes. The posted speed limit is 55 mph.

Here, according to the NTSB, is the sequence of events:

• A 2016 Kenworth truck-tractor semitrailer combination unit operated by  Pioneer Transportation Ltd was traveling in the right lane when it collided with a  2004 Chrysler Sebring,  pushing it into the rear of a 2013 International truck operated by New Pro-Freight Inc.
• As a result of the rear impact, that truck moved forward and collided with the rear of a 2009 Peterbilt truck operated by Schneider National Carriers Inc.
• This collision pushed the semitrailer into the center and left lanes, causing it to collide with a 2016 Subaru Outback which was traveling in the left lane.
• As a result, the Subaru struck a 2016 Ford Explorer.
• A 2018 Toyota Sienna then struck the Subaru and Chrysler, before rolling backward to final rest.
• The Chrysler came to rest in the center lane between the New Pro-Freight semitrailer and the Pioneer truck-tractor, where a post-crash fire ensued, which consumed the Chrysler. The New Pro-Freight semitrailer, Pioneer truck, Subaru, and Toyota also sustained fire damage. Each of the seven vehicles was occupied by a driver only.

The driver of the Chrysler died, while the remaining six drivers sustained minor injuries.

One vehicle was stopped, others doing 55 mph

According to data obtained from various vehicle recording modules, the New Pro-Freight truck was stopped, and the Toyota was traveling 52 mph just prior to the crash.Additional data sources are being examined. When interviewed, the Schneider truck driver reported that he was stopped at the time of the crash, the Subaru and Ford drivers reported traveling 50–55 mph, and the Pioneer truck driver stated that he did not recall the crash event.

The NTSB is gathering various records regarding the Pioneer truck driver’s medical certification and use of portable electronic devices. Initial toxicology results received by the Illinois State Police were negative for alcohol and other drugs. Further testing for prescription and other impairing drugs is underway. Preliminary information suggests that the Pioneer driver was operating within the regulated hours of service, having been on duty for just over 5 hours at the time of the crash.

The drivers' info is being collected

No mechanical defects were identified in the detailed inspection of the Pioneer truck-tractor and semitrailer. Similar information regarding driver qualifications, hours of service, and vehicle maintenance is being gathered for the other two commercial motor carriers involved in the crash.

The NTSB says that “all aspects” of the crash remain under investigation. The agency is working alongside the Illinois State Police, the Illinois Department of Transportation, and the Federal Motor Carrier Safety Administration to compile a complete and accurate account of the crash.