|Type I barriersa||d6||144||380||44||78||R114||R63||R47||R90||R37||R55||R105||30||62||40||1,293|
|Type II barriersb||0||78||120||19||18||18||R21||16||32||15||31||R23||17||10||10||429|
|All other typesc||N||2||31||R1||R3||R10||R4||R26||R7||R2||R2||1||4||4||19||108|
|Cost (2001 $ millions)||N||187||716||101||165||213||135||127||181||75||140||205||97||124||98||2,564|
KEY: N = data do not exist; R = revised.
a A Type I barrier is built on a new highway project or a physically altered 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.
Twenty-eight miles of barriers, while assigned a year of construction, cannot be assigned a cost. Data are produced on a 3-year cycle.
California and Arizona did not provide data for the years 1999, 2000, and 2001 and therefore these years may not be comparable with previous years.
U.S. Department of Transportation, Federal Highway Administration, Office of Environment and Planning, Highway Traffic Noise Barrier Construction Trends (Washington, DC: 2003), tables 1 and 3.