No turn on red

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Some regions normally allow turns on red at most intersections (w:Turn on red), for instance right turn in a right-hand-drive regions, or left turns into one-way streets.

In these regions, some intersections explicitly prohibit turns on red, for reasons of road geometry, safety, policy, etc.

There are several ways such prohibitions have been entered in OpenStreetMap. This list aims to document them, without judging which is best.

restriction=no_turn_on_red

MUTCD/R#R10: Traffic_Signal and MUTCD/California/R#R13: No Turn on Red suggest:

In Talk:Relation:restriction#No_Turn_On_Red, concern was raised in 2016 that OSRM was interpreting these as full-out turn prohibitions, presumably following the instruction previously found in Relation:restriction that "If the first word is "no_", then no routing is possible from the "from" to the "to" member." This issue was fixed in OSRM v5.16.0; only BRouter makes this assumption as of 2021.

restriction:conditional

Created in Toronto instead of restriction=no_right_turn_on_red to avoid the OSRM routing problems, not used elsewhere.

red_turn

Red turn, documents use for bicycles, but the tagging scheme could in principle also apply to motor vehicles.

red_turn:right=* does seem to have some use for no-turn-on-red for general road vehicles; most use appears to be in Germany where it is recommended by DE:Tag:highway=traffic_signals#Zusätzliche_Tags; there was some discussion whether a relation would be better in DE_talk:Tag:highway=traffic_signals#Grünpfeil. permission=on_red_right_turn and permission:on_red=right_turn were suggested in 2013 to 2016:

turn signals

Proposed features/turn signals, a draft from 2016, suggests adding information to the node with highway=traffic_signals at the stop line. The syntax is traffic_signals:turn[:<transportation mode>][:<direction>]=<turn-value>[;<turn-value>][|<turn-value>][|<turn-modifier-value>], with relevant turn-modifier-value being none_on_red, not_right_on_red, or not_left_on_red.

Combinations in use as of August 2021, as found by Taginfo, are:

The most commonly used tag traffic_signals:turn:forward=all|not_right_on_red appears to be used almost exclusively in Boston.