Buying additional trains for the network is a good investment with long-term as well as short-term benefits. Obviously more trains means more services can be run. (Of course, having enough trains is not the only factor that determines service levels. There have to be enough drivers; there also have to be enough "paths" on the track. For more details see the policy on track amplifications.)

When deciding which type of train to buy, Smart Passengers advocates the following criteria:

• Reliability - it's no good buying a train if it's going to be unavailable for service for large amounts of time. For this reason it's a good idea to buy a design which has been proven in service in other cities - including from overseas.
• Suitability - the conditions of Melbourne's system must be taken into account. This includes technical aspects of our track and electrical systems, layout of our stations and behavioural patterns of our commuters. Extensive testing should take place under a wide range of conditions before the trains are accepted into service.
• Good design principles - in safety, security, comfort, capacity and accessibility, new trains should be equal to or better than current trains.
• Contractual safeguards - the manufacturers should be made subject to financial penalties if the trains develop faults after being declared ready for service. The penalties should be structured in a way to encourage them to bring everything they have to bear on the problem, in order to have it fixed as quickly as possible. These conditions may scare some manufacturers away from bidding, or at least charge much more, but this is worthwhile if it means we avoid a debacle like what happened with the Siemens trains in early 2007.
• Long working life - we can't afford to buy trains which will only last 15 years.
• Maintenance arrangements - with modern equipment it is usually best for the manufacturers to provide maintenance for its entire working life.

Obviously it is highly unlikely that all these criteria will be met by any one manufacturer. But we should be basing our decision on these sorts of things rather than just on price.