As in most Western cities, commuter cycling in Melbourne saw a dramatic decline in popularity during the 20th century with the coming of mass car-ownership and the resulting urban sprawl, metropolitan Melbourne being one of the lowest density major cities in the world. In addition to this, the introduction of mandatory helmet legislation (MHL) in the state of Victoria in the early 1990s, the first such legislation in the developed world, further exacerbated the decline in cycling's popularity (see below). However, in the 21st century, cycling for health, fitness, and as a non-polluting alternative to the automobile has begun to increase in popularity once again, though still not back to the pre-MHL levels: cycling's transport modal share accounts for less than 2% of all trips throughout the Melbourne metropolitan area, though bicycles comprised 16% of all morning peak-hour commuter vehicles entering the CBD in March 2017 – up from 9% in March 2008.
