The council's annual 'TravelWise' campaign is being intensified, and will focus on young families after research showed they were the group most likely to change their behaviour.
The initiative is based around the seasons - cycling will be promoted as an alternative form of transport by plugging the region's cycle path network through the summer, and walking will be promoted in the run-up to the start of the school year.
'We will team up with retailers to target children and parents,' said Hertfordshire senior comms officer Sarah Junik.
A media relations programme entitled 'Get fit Herts' will run alongside the main campaign, targeting local press and radio.
Geronimo PR won a ten-month contract to handle the brief after pitching against St Albans-based Communications Management.