A man was killed when his car crashed into a tree stump on the roadside near Hemel Hempstead.
Officers are appealing for information following the incident in Nettleden Road on Saturday, October 6.
For reasons unknown at this stage, a black Vauxhall Zafira, left the road before the collision at around 9.15am.
The driver, a man in his 30s, died as a result of the crash.
Sergeant Keith Evans from the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit, said: “Our thoughts are with the man’s family who are being supported by specially trained officers.
“I would like to hear from anyone who saw the collision, including the events leading up to it, and anyone who has other information that can help with the investigation.
“Similarly, if you have dash cam footage you think may be useful, I would like you to get in touch. If you can help please contact me on the non-emergency number 101 or through email at Keith.Evans@herts.pnn.police.uk, quoting ISR 245 of October 6.”
You can also report information online at https://www.herts.police.uk/Report.
Alternatively, you can contact the independent crime-fighting charity Crimestoppers anonymously on 0800 555 111 or through their Anonymous Online Form at www.crimestoppers-uk.org. No personal details are taken, information cannot be traced or recorded and you will never need to go to court.