We sought to synthesize evidence of the health effects of construction of new roads by systematically reviewing observational studies of such effects. We included and critically appraised 32 studies. The review suggested that out-of-town bypasses decrease injuries on main roads through or around towns, although more robust evidence is needed on effects on secondary roads. New major urban roads have statistically insignificant effects on injury incidence. New major roads between towns decrease injuries. Out-of-town bypasses reduce disturbance and community severance in towns but increase them elsewhere. Major urban roads increase disturbance and severance. More robust research is needed in this area, particularly regarding effects of new roads on respiratory health, mental health, access to health services, and physical activity.