Strategic Versus Simplistic Noise Modelling of the Bay Area of California: Comparing the Impact on Policy and the Community

Many levels of government have strategic planning schemes for the growth of cities and regional areas. Regarding transport noise, planning schemes often define zones to either restrict development, or to ensure new or upgraded developments are constructed in a manner that protects the inhabitants by limiting transportation noise intrusion. The California Building Code defines external noise criteria used to trigger the need for an acoustic assessment and potential building treatments to limit noise ingress. To assist the public in identifying which properties are impacted, local governments provide maps based on basic noise modelling, or simple set-back distances away from major transport routes. This approach ignores the value of terrain and topographical features in screening transport noise, potentially placing many properties incorrectly within impacted zones, adding unwarranted acoustic assessment costs. Two road traffic noise models of the California Bay Area have been built. The first holds road sources only to replicate noise categories published by local authorities, while the second model adds buildings and terrain throughout the 13,000 mi2 area. A comparison between the two methods demonstrates the reduction in the number of properties incorrectly zoned, removing the need for an acoustic assessment at these properties, lowering planning and/or construction costs.