Transportation Policy & Practice # 2
Nation’s Road Capacity:
How Fast is it Growing?
of highway capacity expansion often claim that road
building is lagging far behind. The statistic they use to support this argument is that
lane miles of roadways have grown by only two percent
since 1990. But
once we ‘decode’ this figure, it is clear that
this is an inaccurate way to assess the capacity of
our surface transportation infrastructure.
1990 to 2000, lane miles of all roadways in the United
States grew by slightly less than 2 (1.8) percent. The number is startlingly small, especially given the
large increases in funding made available for surface
transportation through the federal transportation laws
ISTEA and TEA-21.
How could this be?
It turns out that the figure greatly misrepresents
the capacity of the nation’s roadway system.
A closer look at the numbers from the Federal
Highway Administration (FHWA) reveals why.
the Roads Are
most of the population lives in built-up areas and
most driving occurs in these same areas, the vast majority
of roads are in rural areas. According to the latest numbers from the FHWA, nearly 77
percent of the 8,223,393 lane miles of roads in the
U.S. were located in rural areas in 2000.
While the United States has a rural history,
for the last century most of the population has lived
in cities, suburbs, and towns.
Statistics from the Federal Highway
Administration show that in 2000 more than 72 percent
of the population lived in ‘urban’ areas (defined
as central cities, towns, or urban clusters with a
population of greater than 5,000 people and areas
contiguous to that central place).
More importantly, most (61 percent) of the
miles driven in the U.S. are on urban roads.
(see table, next page)
Capacity Is Growing
completion of the Interstate system neared, investment
in new roadway capacity to serve built-up areas
where the majority of people live and drive has increased.
So that while roadway capacity in rural areas
has not grown, roadway capacity in metro
areas has grown markedly, averaging more than
22,000 additional lane miles each year during the
last decade. New
numbers from FHWA show that lane miles of roadway in
urban areas grew by more than 13 percent from 1990 to
some of the growth of the urban road network was due
to re-classification, new roads and widenings
accounted for 69 percent of the total growth.
Because there are so many more miles of roadway in
rural areas, this significant investment does little
to move the total road mileage for the entire country.
As a result, the national figure of 2 percent
road growth has little relevance in a discussion
of needed capacity.
it must be noted that rural roads, even with no
capacity increase in recent years, are still far from
carrying the volumes of traffic they were designed
to. On a
mile-per-mile basis, rural roads carry only 20 percent
as much traffic as urban roads.
Even if the number of miles driven on rural
roads grew 250 percent, rural roads would carry only
half as much traffic on a per-mile basis as urban
roads. Transportation planners have not built new roads in rural
areas because there is generally no need to increase
Why Are Our Roads So Congested?
discussion begs the question, given that roadway
mileage in urban areas has been growing significantly,
why does traffic congestion seem to be so much
has more to do with our growing reliance on driving
for daily tasks. For more on this, see Easing the
Burden or Why Are the Roads So Congested?
on STPP’s website at www.transact.org.