The tram circuit opened on Saturday.
Although two historic trams imported from Australia to run in a clockwise direction on the 15-minute circuit are unlikely to travel faster than 10km/h, Mr Dalzell said they would be too heavy to stop quickly to avoid potential collisions.
"Plus, if the rails are wet they require a greater distance to slow down and stop."
Both trams have front and rear indicators, and warning gongs which ring when they pull out in the road after leaving each of four stops on the circuit.
The trams are being managed by the operator of Christchurch's 2.5km tourist tramway, which is closed because of earthquake damage.
The only accident reported from that operation involved a pedestrian walking into a stationary tram while talking on a cellphone.
Advocates of a tramway extension from the waterfront to Western Springs are meanwhile gathering signatures to a petition calling on Parliament to consider whether legislation will be needed for such a project.