Penalize ways with bicycle=discouraged

[davidmurray]

See discussion here: https://github.com/chairemobilite/transition/pull/950

With the function way:get_value_by_key("bicycle")

Possible example (untested!)

function safety_handler(profile, way, result, data)
  -- convert duration into cyclability
  if profile.properties.weight_name == 'cyclability' then
    local safety_penalty = profile.unsafe_highway_list[data.highway] or 1.
    local is_unsafe = safety_penalty < 1

    -- primaries that are one ways are probably huge primaries where the lanes need to be separated
    if is_unsafe and data.highway == 'primary' and not data.is_twoway then
      safety_penalty = safety_penalty * 0.5
    end
    if is_unsafe and data.highway == 'secondary' and not data.is_twoway then
      safety_penalty = safety_penalty * 0.6
    end

    local forward_is_unsafe = is_unsafe and not data.has_cycleway_forward
    local backward_is_unsafe = is_unsafe and not data.has_cycleway_backward
    local is_undesireable = data.highway == "service" and profile.service_penalties[data.service]
    local forward_penalty = 1.
    local backward_penalty = 1.
    if forward_is_unsafe then
      forward_penalty = math.min(forward_penalty, safety_penalty)
    end
    if backward_is_unsafe then
      backward_penalty = math.min(backward_penalty, safety_penalty)
    end

    if is_undesireable then
      forward_penalty = math.min(forward_penalty, profile.service_penalties[data.service])
      backward_penalty = math.min(backward_penalty, profile.service_penalties[data.service])
    end

+   -- Add penalty for bicycle=discouraged tag
+   local bicycle_tag = way:get_value_by_key("bicycle")
+   if bicycle_tag == "discouraged" then
+     forward_penalty = forward_penalty * 0.5
+     backward_penalty = backward_penalty * 0.5
+   end

    if result.forward_speed > 0 then
      -- convert from km/h to m/s
      result.forward_rate = result.forward_speed / 3.6 * forward_penalty
    end
    if result.backward_speed > 0 then
      -- convert from km/h to m/s
      result.backward_rate = result.backward_speed / 3.6 * backward_penalty
    end
    if result.duration > 0 then
      result.weight = result.duration / forward_penalty
    end
  end
end

Originally posted by @davidmurray in https://github.com/chairemobilite/transition/issues/950#issuecomment-2122688947