The 40 is generally closed top, although the 50s have a mix of closed top, part open top and open top (part open top has a fixed roof for about 40% of the top deck, the remainder being permanently open)
The 50 is open top all year round. The three half tops operate all year and during the school summer holidays the six convertibles have their roofs removed when the frequency increases to half hourly. No journeys on the 50 are booked for closed top although the winter PVR is 3 so inevitably closed tops do cover for the half tops in the winter. Also, we generally run the last two round trips from Swanage at 1725 & 1825 with closed tops in the winter.
The 40 is closed top all year although if open tops have been in Poole for maintenance or breakdowns, they are sometimes sent back to Swanage on early morning or late night 40s.