On Saturday, Phil Wheeler, Executive member for transport and infrastructure on Edinburgh Council, had a letter in the Scotsman. Here are responses to the points he makes:

• In San Francisco, Seattle and Salzburg, passenger numbers increase by 10-18% whenever diesel buses are replaced with trolleybuses - this figure could be higher with the visually-appealing trolleybuses found in cities such as Lyon and Milan.
• The trolleybus network currently planned for Leeds will indeed cost hundreds of millions of pounds, but far from having a "lower return on investment" than trams, the cost benefit ratio is over 2.5. This is significantly higher than for the Leeds "Supertram" scheme previously denied funding by the English Department for Transport.
• Cllr Wheeler suggested that trolleybuses are not trustworthy because they can steer round obstructions and run without wires for short distances. Wires are a "permanent public transport solution" and trolleybuses would only be diverted from them when strictly necessary.
• The benefits of trolleybuses may be "less-enticing" - but not by much. According to West Yorkshire Metro, the Leeds trolleybus network will "deliver many of the congestion-busting benefits that Supertram would have provided, with greater flexibility for future extension into other areas".