adjust speeds to universally use 4/5th of the free-flow speed as expected avg speed

- this is a workaround until we get more thourough work done on the cost model
- this is related to #955 and #989

profiles/car.lua

@@ -46,7 +46,7 @@ local abs = math.abs
 local min = math.min
 local max = math.max
 
-local maxspeed_reduction = 0.66
+local speed_reduction = 0.8
 
 local function find_access_tag(source,access_tags_hierachy)
   for i,v in ipairs(access_tags_hierachy) do
@@ -172,7 +172,7 @@ function way_function (way)
 
   if way.speed == -1 then
     local highway_speed = speed_profile[highway]
-    local max_speed = parse_maxspeed( way.tags:Find("maxspeed") )*maxspeed_reduction
+    local max_speed = parse_maxspeed( way.tags:Find("maxspeed") )
     -- Set the avg speed on the way if it is accessible by road class
     if highway_speed then
       if max_speed > highway_speed then
@@ -244,8 +244,8 @@ function way_function (way)
   end
 
   -- Override speed settings if explicit forward/backward maxspeeds are given
-  local maxspeed_forward = parse_maxspeed(way.tags:Find( "maxspeed:forward"))*maxspeed_reduction
-  local maxspeed_backward = parse_maxspeed(way.tags:Find( "maxspeed:backward"))*maxspeed_reduction
+  local maxspeed_forward = parse_maxspeed(way.tags:Find( "maxspeed:forward"))
+  local maxspeed_backward = parse_maxspeed(way.tags:Find( "maxspeed:backward"))
   if maxspeed_forward > 0 then
     if Way.bidirectional == way.direction then
       way.backward_speed = way.speed
@@ -261,6 +261,12 @@ function way_function (way)
     way.ignore_in_grid = true
   end
   way.type = 1
+
+  -- scale speeds to get better avg driving times
+  way.speed = way.speed * speed_reduction
+  if maxspeed_backward > 0 then
+    way.backward_speed = way.backward_speed*speed_reduction
+  end
   return
 end