A four-car crash and a multi-emergency response - the team must act quickly to piece it together. And after a single-vehicle crash on the M4 on Christmas Day, they are suspicious that there is more to it than meets the eye, and turn to science to get to the truth.

Could CCTV reveal the truth behind a fatal motorbike crash? And after a three-car crash in heavy rain, the team are left stunned by what they discover.

Following the work of Gwent Police's Collision Investigation Unit, the team are alerted to a serious crash by the latest in-car technology, and turn to 3D laser scanning to help establish the facts of what happened. And after a van crashes into a bus shelter, they must find and interpret the evidence to solve the mystery of why the driver lost control.

When a tractor crashes into a family car on a busy city street, officers search for the truth behind the lies and get more than they bargained for when they reconstruct the events of the night.

As two young children fight for their lives after their family car is hit by a van on the M4 motorway, the team focus on finding the scene evidence to reveal the devastating truth behind this crash.

When a motorcyclist dies in a crash at a busy city junction, the race is on to find out how the collision unfolded. A man waiting at a bus stop has a lucky escape after a driver loses control.

When a head-on crash leaves a grandfather dead, Chris discovers the answers could lie in electronic data within the car. As his mission to access it begins, he unearths an intriguing story of what really led up to the crash.

The Crash Detectives are called in to investigate a hit-and-run that leaves a cyclist fighting for her life, while mystery surrounds the death of a delivery driver on a busy dual carriageway.

When calls start coming in to report debris on the M4 motorway, police discover that a father and son have been in a serious crash. As traffic chaos builds, the pressure’s on for the collision team to find out why the car left the road.

When a Friday evening trip out in the car ends in a fatal crash, the driver refuses to accept his driving is to blame. The collision team must find the evidence to prove the real story of the night.

It’s Friday night, and desperate 999 calls start flooding in to report a car travelling the wrong way along the motorway - but it still ends in tragedy. A motorbike and van collide in a busy city centre, but the story isn’t as clear as it first seems.

When a man is found dead on a dark mountain road, there’s no sign of a vehicle. With just fragments of debris for clues, the pressure is on to track down the driver that’s fled the scene.

A road worker is hit by a modified car during a police pursuit. However, when the driver fails to stop, the race is on to track the car down and bring the offender to justice.

When a cyclist dies just nine minutes into a time trial on a dual carriageway, a van driver’s arrested. But a single mark on the road surface raises more questions than answers.