The Alliance is urging people to wear a mask both on board on public transport and in bus stations and transport hubs.
The campaign comes as a reminder as West Yorkshire entered Tier 3 on Wednesday at the end of the second national lockdown.
It will be promoted across the bus network urging people to “keep yourself and those around you safe this Christmas” by wearing a face covering to help to stop the spread of the virus.
Councillor Kim Groves, Chair of the West Yorkshire Combined Authority Transport Committee, said: “The message is simple, please wear a face covering unless you are exempt.
“Whilst most people are adhering to the rules, through this latest campaign we want to encourage everyone to help protect themselves and those around them by wearing a face covering when travelling across West Yorkshire by public transport.
“We have been reminding passengers for months to wear face coverings and this latest campaign highlights the importance of reducing infection in the run up to Christmas and in the winter months.”
The Bus Alliance is a partnership of the West Yorkshire Combined Authority and local bus operators who are tasked with improving bus travel across the region.
Local Police Community Support Officers will be assisting on the ground and helping to reinforce the important message that wearing a face covering is mandatory, except for those with certain health conditions and children under the age of 11, for the entirety of people’s journeys.
Failure to wear a face covering on public transport can result in a fine of up to £6400.
Patrick Sibley, Area Managing Director of Arriva Yorkshire and Yorkshire Tiger, said: “Arriva has seen good levels of face covering compliance from the majority of our passengers since this was mandated by the government in June this year.
“However, there is still a need to focus on this key COVID19 safety measure, particularly as we approach the festive period.
"We believe this latest campaign, which is focussed on reiterating key guidance around the requirement for customers to wear face coverings, will further support the continued efforts to reduce the impact of COVID19 across the region.”
The Combined Authority and bus operators have put in place additional measures to ensure that passengers are able to travel safely across the transport network which include social distancing signage and seating guidance, enhanced cleaning and sanitising of buses and stations focusing on contact points, and the removal of some seating at bus stations to help passengers to social distance.
Martin Hirst, Commercial Director of First West Yorkshire, said: “We’ve seen the benefits and confidence in safety that wearing a face covering gives to everyone using our buses.
"The majority of our customers are complying and this has remained so as more people travel, which is great to see and the right thing to do, so we encourage our customers to carry on, wear one and support this campaign.”
Alex Hornby, CEO at Transdev, said: “Together bus operators in West Yorkshire are pleased to have seen so many customers embracing the need to wear face coverings since these became mandatory earlier in the year.
"We are sure everyone appreciates the need for us to continue to talk about face coverings and the benefits they bring, to make sure the numbers of customers wearing them remains high.
"We believe our joint campaign will ensure buses remain clean and safe for customers, as more people begin to travel after this latest lockdown and over the festive period.”