Support OSM traffic signal directions (#6153)

Currently OSRM parses traffic signal nodes without consideration
for the direction in which the signal applies. This can lead
to duplicated routing penalties, especially when a forward and backward
signal are in close proximity on a way.

This commit adds support for directed signals to the extraction and
graph creation. Signal penalties are only applied in the direction
specified by the OSM tag.

We add the assignment of traffic directions to the lua scripts,
maintaining backwards compatibility with the existing boolean
traffic states.

As part of the changes to the internal structures used for tracking
traffic signals during extraction, we stop serialising/deserialising
signals to the `.osrm` file. The traffic signals are only used by
`osrm-extract` so whilst this is a data format change, it will not
break any existing user processes.

profiles/bicycle.lua

@@ -5,6 +5,7 @@ api_version = 4
 Set = require('lib/set')
 Sequence = require('lib/sequence')
 Handlers = require("lib/way_handlers")
+TrafficSignal = require("lib/traffic_signal")
 find_access_tag = require("lib/access").find_access_tag
 limit = require("lib/maxspeed").limit
 Measure = require("lib/measure")
@@ -235,10 +236,7 @@ function process_node(profile, node, result)
   end
 
   -- check if node is a traffic light
-  local tag = node:get_value_by_key("highway")
-  if tag and "traffic_signals" == tag then
-    result.traffic_lights = true
-  end
+  result.traffic_lights = TrafficSignal.get_value(node)
 end
 
 function handle_bicycle_tags(profile,way,result,data)

profiles/car.lua

@@ -6,6 +6,7 @@ Set = require('lib/set')
 Sequence = require('lib/sequence')
 Handlers = require("lib/way_handlers")
 Relations = require("lib/relations")
+TrafficSignal = require("lib/traffic_signal")
 find_access_tag = require("lib/access").find_access_tag
 limit = require("lib/maxspeed").limit
 Utils = require("lib/utils")
@@ -360,10 +361,7 @@ function process_node(profile, node, result, relations)
   end
 
   -- check if node is a traffic light
-  local tag = node:get_value_by_key("highway")
-  if "traffic_signals" == tag then
-    result.traffic_lights = true
-  end
+  result.traffic_lights = TrafficSignal.get_value(node)
 end
 
 function process_way(profile, way, result, relations)

profiles/foot.lua

@@ -157,6 +157,7 @@ function process_node(profile, node, result)
   -- check if node is a traffic light
   local tag = node:get_value_by_key("highway")
   if "traffic_signals" == tag then
+    -- Direction should only apply to vehicles
     result.traffic_lights = true
   end
 end

profiles/lib/traffic_signal.lua

@@ -0,0 +1,26 @@
+-- Assigns traffic light value to node as defined by
+-- include/extractor/traffic_lights.hpp
+
+local TrafficSignal = {}
+
+function TrafficSignal.get_value(node)
+    local tag = node:get_value_by_key("highway")
+    if "traffic_signals" == tag then
+        local direction = node:get_value_by_key("traffic_signals:direction")
+        if direction then
+            if "forward" == direction then
+                return traffic_lights.direction_forward
+            end
+            if "backward" == direction then
+                return traffic_lights.direction_reverse
+            end
+        end
+        -- return traffic_lights.direction_all
+        return true
+    end
+    -- return traffic_lights.none
+    return false
+end
+
+return TrafficSignal
+

profiles/testbot.lua

@@ -4,6 +4,7 @@
 -- Primary road:  36km/h = 36000m/3600s = 100m/10s
 -- Secondary road:  18km/h = 18000m/3600s = 100m/20s
 -- Tertiary road:  12km/h = 12000m/3600s = 100m/30s
+TrafficSignal = require("lib/traffic_signal")
 
 api_version = 4
 
@@ -38,12 +39,9 @@ function setup()
 end
 
 function process_node (profile, node, result)
-  local traffic_signal = node:get_value_by_key("highway")
-
-  if traffic_signal and traffic_signal == "traffic_signals" then
-    result.traffic_lights = true
-    -- TODO: a way to set the penalty value
-  end
+  -- check if node is a traffic light
+  result.traffic_lights = TrafficSignal.get_value(node)
+  -- TODO: a way to set the penalty value
 end
 
 function process_way (profile, way, result)