Table 4-52,,,,,,,,,,,
Highway Noise Barrier Construction  (Miles),,,,,,,,,,,
,,,,,,,,,Total,,
,Unknown,R1970-79,R1980-89,R1990,R1995,1996,1997,1998, 1970-98,,
Type I barriersa,6d,102,419,44,87,34,47,114,"1,146",,
Type II barriersb,0,70,128,19,32,15,31,22,391,,
All other typesc,N,2,28,0,6,0,1,1,79,,
    Total length,6,175,575,63,125,49,78,137,"1,623",,
,,,,,,,,,,,
Cost (1998 $ millions),N,134,656,89,152,60,111,169,"1,931",,
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.,,,,,,,,,,,
,,,,,,,,,,,
KEY: N = data do not exist; R = revised.,,,,,,,,,,,
,,,,,,,,,,,
NOTES:  Miles have been converted from kilometers. Totals may not match the sum of yearly estimates due,,,,,,,,,,,
" to rounding and converting from metric.  24 miles of barriers, while assigned a year of construction, cannot ",,,,,,,,,,,
be assigned a cost. Data are produced on a 3-year cycle.,,,,,,,,,,,
,,,,,,,,,,,
"SOURCE:  U.S. Department of Transportation, Federal Highway Administration, Office of Environment  ",,,,,,,,,,,
"and Planning, HighwayTraffic Noise Barrier Construction Trends (Washington, DC: 2000), tables 1 and 3.",,,,,,,,,,,