diff --git a/simutrans/trunk/boden/grund.cc b/simutrans/trunk/boden/grund.cc
index 77ff320..19552ce 100644
--- a/simutrans/trunk/boden/grund.cc
+++ b/simutrans/trunk/boden/grund.cc
@@ -635,6 +635,9 @@ void grund_t::info(cbuffer_t& buf) const
 	if(get_weg_ribi_unmasked(water_wt)) {
 		buf.printf("\nwater ribi: %i",get_weg_ribi_unmasked(water_wt));
 	}
+	if(is_water()) {
+		buf.printf("\ncanal ribi: %i", ((const wasser_t*)this)->get_canal_ribi());
+	}
 	buf.printf("\ndraw_as_obj= %i",(flags&draw_as_obj)!=0);
 	buf.append("\nclimates= ");
 
diff --git a/simutrans/trunk/boden/wasser.cc b/simutrans/trunk/boden/wasser.cc
index caf9c5f..4b29d18 100644
--- a/simutrans/trunk/boden/wasser.cc
+++ b/simutrans/trunk/boden/wasser.cc
@@ -33,6 +33,16 @@ void wasser_t::prepare_for_refresh()
 }
 
 
+/**
+ * helper function: return maximal possible ribis, does not
+ * take water ribi of sea tiles into account.
+ */
+ribi_t::ribi get_base_water_ribi(grund_t *gr)
+{
+	return gr->is_water() ? (ribi_t::ribi)ribi_t::all : gr->grund_t::get_weg_ribi(water_wt);
+}
+
+
 void wasser_t::calc_image_internal(const bool calc_only_snowline_change)
 {
 	if(  !calc_only_snowline_change  ) {
@@ -52,11 +62,31 @@ void wasser_t::calc_image_internal(const bool calc_only_snowline_change)
 
 		// test tiles to north, south, east and west and add to ribi if water
 		ribi = ribi_t::none;
+		canal_ribi = ribi_t::none;
+		ribi_t::ribi base_ribi = get_base_water_ribi(this);
+
 		for(  uint8 i = 0;  i < 4;  i++  ) {
 			grund_t *gr_neighbour = NULL;
-			if(  get_neighbour( gr_neighbour, invalid_wt, ribi_t::nsew[i] )  ) {
-				if (gr_neighbour->is_water()  ||  (gr_neighbour->get_weg_ribi(water_wt) & ribi_t::reverse_single(ribi_t::nsew[i]))!=0 ) {
-					ribi |= ribi_t::nsew[i];
+			ribi_t::ribi test = ribi_t::nsew[i];
+
+			if( (test&base_ribi)  &&  get_neighbour(gr_neighbour, invalid_wt, test) ) {
+				// neighbour tile has water ways
+				ribi_t::ribi ribi_neigh_base = get_base_water_ribi(gr_neighbour);
+				if ((ribi_neigh_base & ribi_t::reverse_single(test))==0) {
+					// we cannot go back to our tile
+					continue;
+				}
+
+				// set water ribi bit
+				ribi |= test;
+
+				// test whether we can turn on neighbour canal tile
+				if (!gr_neighbour->is_water()) {
+					ribi_t::ribi ribi_orth = ribi_t::doubles( ribi_t::rotate90( test ));
+					if ((ribi_neigh_base & ribi_orth) != ribi_orth) {
+						// turning not possible, mark it as canal ribi
+						canal_ribi |= test;
+					}
 				}
 			}
 		}
@@ -71,4 +101,5 @@ void wasser_t::rotate90()
 {
 	grund_t::rotate90();
 	ribi = ribi_t::rotate90(ribi);
+	canal_ribi = ribi_t::rotate90(canal_ribi);
 }
diff --git a/simutrans/trunk/boden/wasser.h b/simutrans/trunk/boden/wasser.h
index 689554c..0617c74 100644
--- a/simutrans/trunk/boden/wasser.h
+++ b/simutrans/trunk/boden/wasser.h
@@ -12,11 +12,18 @@
 class wasser_t : public grund_t
 {
 protected:
+	/// cache ribis to tiles connected by water
 	ribi_t::ribi ribi;
+	/// helper variable, ribis to canal tiles, where ships cannot turn left or right
+	ribi_t::ribi canal_ribi;
 
+	/**
+	 * This method also recalculates ribi and cache_ribi!
+	 */
 	void calc_image_internal(const bool calc_only_snowline_change);
 
 public:
+
 	wasser_t(loadsave_t *file, koord pos ) : grund_t(koord3d(pos,0) ), ribi(ribi_t::none) { rdwr(file); }
 	wasser_t(koord3d pos) : grund_t(pos), ribi(ribi_t::none) {}
 
@@ -32,6 +39,8 @@ public:
 	// map rotation
 	void rotate90();
 
+	ribi_t::ribi get_canal_ribi() const { return canal_ribi; }
+
 	// static stuff from here on for water animation
 	static int stage;
 	static bool change_stage;
diff --git a/simutrans/trunk/dataobj/route.cc b/simutrans/trunk/dataobj/route.cc
index e92e0e0..6f84e2d 100644
--- a/simutrans/trunk/dataobj/route.cc
+++ b/simutrans/trunk/dataobj/route.cc
@@ -13,6 +13,7 @@
 #include "../simhalt.h"
 #include "../boden/wege/weg.h"
 #include "../boden/grund.h"
+#include "../boden/wasser.h"
 #include "../dataobj/marker.h"
 #include "../ifc/simtestdriver.h"
 #include "loadsave.h"
@@ -492,8 +493,14 @@ bool route_t::intern_calc_route(karte_t *welt, const koord3d ziel, const koord3d
 					// only check previous direction plus directions not available on this tile
 					// if going straight only check straight direction
 					// if going diagonally check both directions that generate this diagonal
+					// also enter all available canals and turn to get around canals
 					if (tmp->parent!=NULL) {
-						k->jps_ribi = ~way_ribi | current_dir;
+						k->jps_ribi = ~way_ribi | current_dir |  ((wasser_t*)to)->get_canal_ribi();
+
+						if (gr->is_water()) {
+							// turn on next tile to enter possible neighbours of canal tiles
+							k->jps_ribi |= ((const wasser_t*)gr)->get_canal_ribi();
+						}
 					}
 				}