Civil Engineering Reference
In-Depth Information
The number of hours each day with congested travel has increased over the
years. In contrast to the typical
s congestion in
large metropolitan areas extends up to 10 h/day, with peak periods lasting 4 h in the
morning (6
“
peak hour
”
of the 1960s, today
'
7 p.m.). Congested travel corridors,
however, tend to experience congestion for longer periods (INRIX 2010), espe-
cially on freeways. Thus the delay duration mirrors the day-to-day traf
10 a.m.), and 4 h in the evening (3
-
-
c patterns.
Midblock and intersection delays in major business districts frequently last
throughout the business day. The delay periods at typical urban signalized inter-
sections usually range from 15 min to more than 1 h, depending on approach
volumes, intersection geometry, and traf
c signal timing.
8.2.2.1 Daily and Hourly Variations
The average daily duration of delay, for typical days of the week (Fig.
8.3
), shows
that Friday experiences the largest amount of delay, and Monday the least; while
Sunday has the lowest delays. And when delay is distributed by time of day
(Fig.
8.4
), the worst hour is 5
6 p.m. in the evening, with about 14 % of the daily
delay, while the hours with the least amounts of delay are from midnight to 6 a.m.
-
8.2.3 Extent
Extent
measures how far congestion is spread (miles of roadways, or route miles
impacted), and how many travelers experience congestion. It varies by city size and
type of facility. In large urban areas it can extend for miles along heavily traveled
corridors or for many blocks at a signalized intersection.
Freeways, which usually account for about half of all urban travel, experience
more delay than arterial streets. The UMR [
9
] found that during peak periods (6
-
10 a.m. and 3
7 p.m.) freeways account for twice as much daily delay as arterial
streets (42 % vs. 21 %); and for the rest of the day (16 h) freeways and arterial
streets account for approximately equal shares of delay (18 and 19 % respectively)
-
Fig. 8.3
Percent of delay by
day of week.
Source
Reference [
15
], p 7. Exhibit 4
