Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 17
17
by making three consecutive right turns. Along some LRT
alignments, there may be few locations where left turns are
permitted across the tracks, which could lead to increased
pressure for motorists to turn left where left turns are possible,
even if they are prohibited. Posting advanced signs showing
motorists that they can accomplish upcoming left turns by
making three consecutive right turns starting beyond the cross
street might help reduce the number of left-turn violations.
This can be iterated in public education materials by including
instructions for accomplishing a left turn by making three suc-
cessive right turns (4).
FIGURE 19 Use of green arrow aspects for through traffic.
SIGNAL DISPLAYS
In-Roadway Lights
Red Left-Turn Arrows
In-roadway lights are defined in the MUTCD (10) as "special
Red left-turn arrows (as shown in Figure 18) provide more
types of highway traffic signals installed in the roadway surface
positive guidance to motorists than red balls. At a few inter-
to warn road users that they are approaching a condition on or
sections in Denver with LRT, where left turns are made from adjacent to the roadway that might not be readily apparent
a one-way street onto another one-way street, left turns on red and might require the road users to slow down and/or come
are not allowed owing to the LRT tracks. In RTD's experi- to a stop" (10). In 2006, Houston METRO began testing an
ence, the red left-turn arrow signal display has worked better application of in-roadway lights to get motorists' attention
than the combination of a red ball and static signs stating "No to stop at the red lights on the cross-street approaches to sig-
Turn on Red." Motorists seem to have more respect for the red nalized intersections with LRT and to reduce encroachment
arrow signal display than the static sign, as they will violate into the intersection. The lights being tested by METRO are
the signs more often than the signals. red, installed along the stop bar, and flicker at a fast rate. An
application of the in-roadway lights at one intersection in
Green Arrow Aspects for Through Traffic
Houston is illustrated in Figure 21, as an LRV approaches
from the right.
In an effort to provide positive guidance, the METRORail
Traffic Safety Assessment report recommended the use of Over the past year, METRO has installed in-roadway
green arrow aspects on traffic signal heads instead of green lights at 11 intersections and experienced only two red-light
balls and redundant turn-prohibition signs (4) (Figures 19 running accidents at the 11 intersections since installation (the
and 20). Coifman and Bertini also recommend the use of green lights have been installed at the intersections on average for
arrow aspects for through traffic to reduce the chance that a about 11 months). This compares with about eight red-light
driver turning left will mistake the through traffic signals for running accidents per year on average at these same inter-
the turning movement, which can happen for a number of rea- sections for the previous 3-year period, a reduction METRO
sons. First, there are generally more through signals than turn views as significant.
arrows. Second, the surface area of the green ball is greater
Although this application was to prevent red-light running
than the surface area of an arrow, making it more prominent.
on the cross street, it could have the same effect, for some align-
Third, the transmittance of a green filter is greater than that of
ments, for left-turning traffic. LACMTA reported that they are
a red filter. For these reasons, the through traffic signal balls
currently considering using the in-roadway lights to mitigate
have a greater probability of being perceived by a driver than
left-turn motorist violations at intersections with LRV.
do the left-turn arrow signals (3). If green arrow aspects are
used for through movements, a green ball should still be used
in the right lane where right turns are permitted across the par-
allel crosswalk pedestrian movement.
FIGURE 18 Use of a red arrow to prohibit the left-turn
movement. FIGURE 20 Use of arrows to control traffic movements.
