Jenkins turned out to help the council publicise the Europe-wide initiative which comes to Cardiff on 22 September and will see St Mary street converted into a pedestrian area.
And the World Record points holder took the opportunity to launch his testimonial year with a 'conversion' of his own outside Cardiff Castle.
Motorists will be encouraged to give up their cars for the day and experience walking and cycling in a city centre area in traffic free comfort and safety.
The initiative is designed to encourage the use of alternative modes of transport to the car; raise awareness of the long term effects of pollution and traffic congestion in our towns and cities; and demonstrate life without traffic in busy city centre locations.
The day will focus on St Mary Street - probably Wales' most polluted street - which will be given over to a range of events for pedestrians and cyclists throughout the day.
People can enjoy a variety of street entertainment and live music in a cleaner and safer environment, whilst being able to obtain information about travelling by bus, rail, cycling or by foot in Cardiff. The street will be closed to traffic from 1am to prepare for the event which will take place from 12 noon to 7pm to attract workers, shoppers and other visitors to the city centre.
"I've spent many happy match days in Cardiff at the Arms Park and the Millennium Stadium when St Mary Street is full of rugby fans and there isn't a car in sight," said Jenkins.
"There's always a special kind of carnival atmosphere and I'm sure that the absence of traffic plays a major part in that, so it will be interesting to sample the atmosphere next Monday."Deputy Leader (Enterprise & Transport), Councillor Michael Michael said: "Cardiff is playing a very active role in this international initiative, and we hope that members of the local community can also play their part by leaving the car at home, using alternative transport, getting on their bikes and enjoying and learning from the St. Mary St. event."