https://en.wikipedia.org/wiki/DART_Light_Rail -> System Length 93 mi (150 km) https://en.wikipedia.org/wiki/Trams_in_Melbourne -> System Length 160 miles (250 kilometres)

However, your point that the decentralization plays a difference is very valid. The Melbourne network is a dense grid which serves a much more compact area whereas the Dallas system consists of a small number of lines that stretch very far out into the low-density suburbs. Hence, far fewer people are near a DART station.