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18 Far-Side Light Rail Vehicle Signals When LRT bar signals are placed in advance of an inter- section (i.e., near-side signals), LRVs are required to stop before reaching the intersection. By installing the bar signals on the far side of the intersections and instructing LRV opera- tors to pull up to the stop bar on a red indication, it establishes an LRV presence at the intersection and could help to reduce illegal left turns (4). TRAFFIC SIGNAL PHASING Traffic signal phasing deals with the order in which the per- FIGURE 21 In-roadway lights in Houston (Courtesy: METRO). mitted and protected movements are allocated at signalized intersections. The following traffic signal phasing schemes have been recommended specifically to mitigate collisions Programmable Visibility Signal Heads between LRVs and motor vehicles. Programmable visibility signal heads reduce the visibility of the signals from adjacent lanes. These signal heads can be All-Red Traffic Signal Phase used to reduce the likelihood that motorists in the left-turn The all-red traffic signal phase holds all vehicular traffic on red lane will cue off the signals for the through traffic (3,4). while the LRV passes through the intersection. The purpose of the all-red phase is to discourage illegal left-turn movements Light Rail Transit Signals with Format across the LRV tracks by prohibiting all movements while the and Color Different from Traffic Signals LRV is present at the intersection. There is evidence to suggest that motorists in the left-turn lanes may cue off of the cross- The use of LRT signals that look similar to traffic signals street traffic in anticipation of a leading left turn, or that they (e.g., colored ball, "T," or "X" signals) tend to confuse may cue off of the parallel through traffic movements or sig- motorists (e.g., motorists may interpret a green "T" signal that nal indications rather than focusing on the left-turn signal indi- is visible from a left-turn pocket as a left-turn arrow). There- cation (1,3). By holding all traffic on red, motorists are less fore, LRT signals should be clearly distinguishable from con- likely to make illegal movements across the tracks. Transit ventional traffic signal displays in terms of format and color agencies including TriMet, LACMTA, and Houston METRO and their indications should be meaningless to motorists with- have implemented all-red phases at signalized intersections out the provision of supplemental signs. LRT bar signals are along their LRT alignment. white, monochrome bar signals that are separated in space from motor vehicle signals (1) (Figure 22). Lagging Left Turns Motorists sometimes initiate their left turns as soon as the cross-street traffic receives the red, but before they receive the green arrow indication (1). This is particularly common at locations with leading left-turn phases, as motorists cue off the cross-street signals in anticipation of the leading left turn [Coifman and Bertini (3) noted that LRT accident reports suggest that this is occurring]. When the leading left-turn sig- nal phase is pre-empted by an approaching LRV, the motorist anticipating the leading left turn could be in conflict with the LRV. Likewise, some motorists will "sneak" through the inter- section at the end of their protected turn phase. When the protected left-turn phase is a leading left turn, this can put motorists in danger of being struck by an LRV approaching during the parallel through traffic's green phase. The use of lagging left turns can mitigate the possibility of FIGURE 22 LRT signals (Courtesy: Jon Bell). collisions in both of these situations. Lagging left turns help