|Type I barriersa||d6||102||419||44||78||113||62||48||87||34||47||114||1,147|
|Type II barriersb||0||70||128||19||18||18||22||16||32||15||31||22||391|
|All other typesc||N||2||28||0||2||11||3||25||6||0||1||1||79|
|Cost (1998 $ millions)||N||134||656||89||144||186||118||112||152||60||111||169||1,931|
KEY: N = data do not exist; R = revised.
a A Type I barrier is built on a highway project to construct a new highway or to physically alter an existing highway.
b A Type II barrier is built to abate noise along an existing highway (often referred to as retrofit abatement) and is not mandatory.
c All other types of barriers are nonfederally funded.
d Have not been assigned a year of construction or a cost.
Miles have been converted from kilometers.
Totals may not match the sum of yearly estimates due to rounding and converting from metric. Twenty-four miles of barriers, while assigned a year of construction, cannot be assigned a cost. Data are produced on a 3-year cycle.
Numbers may not add to totals due to rounding.
U.S. Department of Transportation, Federal Highway Administration, Office of Environment and Planning, Highway Traffic Noise Barrier Construction Trends (Washington, DC: 2000), tables 1 and 3.