Not much of a surprise
A 2014 study published in Environmental Health Perspectives, “The Societal Costs and Benefits of Commuter Bicycling: Simulating the Effects of Specific Policies Using System Dynamics Modeling,” looks at four options for increasing cycling in the city of Auckland, New Zealand.
The four policy options analyzed were: (1) The creation of a regional cycling network (RCN), currently being pursued by the Auckland Regional Council. It involves marked lanes with no physical segregation on 46% of main roads, 25 kilometers of shared footpaths per 100,000 population and a small number of shared bus and bicycle lanes. (2) Arterial segregated bicycle lanes (ASBL), with one-way, barrier-separated cycling lanes on all main roads throughout the region. (3) Self-explaining roads (SER), which slow car traffic through structural changes and visual cues. (4) A combination of arterial segregated bicycle lanes and self-explaining roads (ASBL+SER).
Compared to the business-as-usual scenario, all four alternative policies had positive cost-benefit ratios, ranging from $6 to $24 saved for every $1 spent. The number of cyclist deaths and injuries increase under all the options, but the overall rates fall because of the rise in cycling mode share. The total number of deaths also falls, primarily through a drop in car-crash fatalities and an increase in physical activity and health.
There is much more at the link, including graphs!!