From b6a9e2e1a4470e324e88b863917996b01a334e82 Mon Sep 17 00:00:00 2001
From: Dustin Carlino <dabreegster@gmail.com>
Date: Thu, 26 Jul 2018 17:08:49 -0700
Subject: [PATCH] dont make u-turns unless really at a dead-end

---
 map_model/src/intersection.rs | 13 ++++++++++++-
 map_model/src/make/turns.rs   |  7 +++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/map_model/src/intersection.rs b/map_model/src/intersection.rs
index ca479b42dd..94ca6b4379 100644
--- a/map_model/src/intersection.rs
+++ b/map_model/src/intersection.rs
@@ -3,7 +3,8 @@
 use dimensioned::si;
 use geom::Pt2D;
 use std::fmt;
-use {LaneID, TurnID};
+use {LaneID, TurnID, RoadID, Map};
+use std::collections::HashSet;
 
 // TODO reconsider pub usize. maybe outside world shouldnt know.
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
@@ -33,3 +34,13 @@ impl PartialEq for Intersection {
         self.id == other.id
     }
 }
+
+impl Intersection {
+    pub fn is_dead_end(&self, map: &Map) -> bool {
+        let mut roads: HashSet<RoadID> = HashSet::new();
+        for l in self.incoming_lanes.iter().chain(self.outgoing_lanes.iter()) {
+            roads.insert(map.get_l(*l).parent);
+        }
+        roads.len() == 1
+    }
+}
diff --git a/map_model/src/make/turns.rs b/map_model/src/make/turns.rs
index 5512aae6cb..22f1ad7d1b 100644
--- a/map_model/src/make/turns.rs
+++ b/map_model/src/make/turns.rs
@@ -107,20 +107,19 @@ fn make_turns(
         assert_eq!(map.get_l(*l).src_i, parent);
     }
 
-    let dead_end = incoming.len() == 1 && outgoing.len() == 1;
+    let dead_end = map.get_i(parent).is_dead_end(map);
 
     let mut result = Vec::new();
     for src in incoming {
         let src_l = map.get_l(*src);
-        let other_side = map.get_r(src_l.parent)
-            .get_opposite_lane(src_l.id, src_l.lane_type);
 
         for dst in outgoing {
             let dst_l = map.get_l(*dst);
             // Don't create U-turns unless it's a dead-end
-            if other_side == Some(dst_l.id) && !dead_end {
+            if src_l.parent == dst_l.parent && !dead_end {
                 continue;
             }
+            // TODO if it's a multi-lane dead-end, ideally match up lanes or something
 
             result.push(Turn {
                 id: TurnID::new(*src, *dst),