Measuring Traffic Congestion - Road Traffic Congestion - page 100

ow freeway speed as a threshold for congestion, has the
advantage of simplicity in data analysis and in tracking area wide trends, its utility
in evaluating traf

While using free- fl

c congested conditions in large metropolitan areas is questionable
because it is nearly impossible to build the capacity necessary to serve peak hour
traf ow speeds (e.g., lack of space for new roadways, social and

environmental constraints).
A more realistic standard of delay metric should re

c demands at free- fl

fl ect goals that are actionable

in terms of social, environmental and ected

in Tables 8.2 , 8.3 and 8.4 , and through approaches described for the New York
Metropolitan area (NYMTC); Washington State DOT; and for the greater Montreal
region where congestion thresholds were established to re

financial constraints. These are best re fl

fl ect local conditions/

expectations.
Traf

c congestion has many impacts. These impacts include (1) longer and less
reliable trip times (Chap. 9 ) , (2) decreased mobility (Chap. 10 ), decreased acces-
sibility (Chap. 11 ), lower roadway productivity (Chap. 12 ) , and increased costs and
environmental effects (Chap. 13 ). These are discussed in the chapters that follow.

References

1. McClintock M (1925) Street traffic control. McGraw-Hill Book Company Inc, New York
2. Altshuler A, Womack JP, Pucher JR (1979) The urban transportation system — politics and

policy innovations. The MIT Press, Cambridge, MA
3. Homburger WS, Hall JW, Loutzenhouser HC, Reilly W (1996) Fundamentals in traf c
engineering. Institute of Transportation Studies, University of California Berkeley, California
4. Meyer MD (1993) A toolbox for alleviating traf c congestion and enhancing mobility.
Institute of Transportation Engineers, Washington, DC
5. Lisco T, Draft Memorandum to Palewonsky L (1999) RE: AM peak period traf c volumes
travel times and speeds on interstate 93. Between Medford and Boston, s.n., 1992 - 1994 and
1998 - 1999
6. Lomax T, Turner S, Shunk G, Levonson HS, Pratt RH, Douglas B (1997) NCHRP 398:
quantifying congestion, vol 2. Transportation Research Board, National Research Council,
Washington, DC. User ' s guide
7. Lomax T, Turner S, Shunk G, Levinson HS, Pratt RH, Bay P, Douglas B (1997) NCHRP
report 398:quantifying congestion, vol 1. Transportation Research Board, National Research
Council, Washington, DC. Final report
8. New York Metropolitan Transportation Council (2009) Congestion management process

—

2009 status report. New York, s.n.
9. Lomax T, Schrank D, Turner S, Geng L, Li Y, Koncz N (2010) 2010 urban mobility report.
Texas Transportation Institute, University Transportation Center for Mobility, s.l.
10. Cambridge Systematics, Dowling Associates, System Metrics Group (2008) NCHRP report
618: cost effective performance measures for travel time delay, variation, and reliability.
Transportation Research Board, Washington, DC
11. INRIX (2011) National traf c scorecard 174

12. City of Chicago study and recommendations for improving traf c movement in the central
business district (1950) The Mayor

— 2010 Annual Report. pp 163

-

' s Traf c Survey Committee for the Central business

District, s.l.