Bus ticket machine data revealed no change to prom queues in 2018
The infrastructure minister insists the horse trams don't have an impact on traffic at peak times during TT.
Last year, the Department of Infrastructure suspended services between 5pm and 6pm when roads were closed in a bid to reduce queues on Douglas promenade.
Ray Harmer was asked at this month's sitting of Tynwald how effective the change had been, but revealed data from bus ticket machines showed no difference.
The machines have GPS within to track the movements of public transport vehicles.
The minister believes parking causes more delays than the horse trams: