Families are being invited to join Thomas the Tank Engine and help raise money for people affected by autism.
The National Autistic Society is running "Train Walks" across the UK from the 5th to the 8th of June.
There are more than 150 Thomas & Friends™ themed sponsored Train Walks planned across the country.
As well as a fun day out for the whole family, Train Walk will help raise vital funds for people with autism and their families.
If there isn't a Train Walk happening near you, people are being encouraged to organise their own.
Naomi Wilkinson, presenter of Five's Milkshake!, is backing the campaign.
She says: "Train Walks are a fantastic way to raise much needed funds for people with autism, a disability which affects over half a million people in the UK. What a great chance to have a brilliant day out – come on people, let's get walking!"
Autism is a brain development disorder which commonly affects social interaction and communication.
The condition can vary widely and scientists say a significant number of children with autism and related disorders could be undiagnosed.
Often families need help to find the right diagnosis and support for children on the autistic spectrum.
The National Autistic Society says £15 helps pay for a helpline advisor to send information about autism support to five worried parents.
Just £25 pays for the first stage of training a National Autistic Society befriender, who can help support families affected by autism.
£75 pays for three families to attend the National Autistic Society Earlybird programme that provides help and support to pre-school children with autism.
And £100 helps pay for a full diagnosis of a child at the National Autistic Society assessment centre.
To find your nearest Train Walk, or to find out how to organise your own, visit www.autism.org.uk/trainwalk