Insufficient Capacity, Growth in Population, Employment, and Car Use - Road Traffic Congestion - page 55

Therefore the metro area VMT per capita increases as suburban population
growth exceeds center city population growth.

6.2.3.2 Increasing Employment

Employed persons make more trips and travel longer distances than those who are
not working (Table 6.8 ).
While workers constitute about 50 % of the US population, they account for
approximately 83 % of the vehicle miles of travel.

It is not (only) their work trips
that cause this substantial difference (but also) the other trips and activities engaged
in by the working population

“

— on the way to and from work, caring for their

families, etc. ([ 3 ], p. 6).

This is clearly demonstrated in Fig. 6.6 ([ 3 ], Fig. 1-6, p. 7). This

”

gure shows

that the workers ' travel share by hour of day constitutes the major component of all

travel.
However, just as an increase in employment increases travel demand, a decrease
in employment reduces travel demand. As a result of the economic slowdown
(2007

c Scorecard ([ 10 ], p. A-1) in fact
reported a reduction in congestion of 12.7 % for the top 100 metropolitan areas that
experienced an aggregate employment loss of 5.8 % from 2006 to 2010.

- 2010), the INRIX 2010 National Traf

Table 6.8 Worker and non-worker travel demand, 2001
Daily trips per person Daily miles driven per person

Employed 4.5 35.5

Not employed 3.7 16.0

All persons (15 years and older) 4.1 29.1

Source Reference [ 8 ], Tables A-9 and A-17

Fig. 6.6 Worker and non-worker shares of travel by time of day. Source Reference [ 3 ],
Transportation Research Board, “ Commuting in America III ” , Fig. 1-6, p. 7