The commission, which may be extended for a further two years, includes a range of studies such as developing a business case for major regional bus schemes.
The consultancy will develop public transport plans, redesign interchanges and review ticketing, retail and customer care strategies. It will train and develop staff from both organisations.
Nexus interim services director Ken Kemp said: "We are taking an in-depth look at how we can improve the quality and ease of use of public transport across Tyne and Wear."
