From 7b5086840616e427ac35e440d5d573125c10eee7 Mon Sep 17 00:00:00 2001
From: namdre <jakob.erdmann@dlr.de>
Date: Fri, 14 Sep 2018 23:30:30 +0200
Subject: [PATCH] fix #4600

---
 src/od/ODMatrix.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/od/ODMatrix.cpp b/src/od/ODMatrix.cpp
index 60f6e1f28762..55ab35db5ca0 100644
--- a/src/od/ODMatrix.cpp
+++ b/src/od/ODMatrix.cpp
@@ -309,13 +309,16 @@ ODMatrix::writeFlows(const SUMOTime begin, const SUMOTime end,
     for (std::vector<ODCell*>::const_iterator i = myContainer.begin(); i != myContainer.end(); ++i) {
         const ODCell* const c = *i;
         if (c->end > begin && c->begin < end) {
+            const double probability = asProbability ? float(c->vehicleNumber) / STEPS2TIME(c->end - c->begin) : 1;
+            if (probability <= 0) {
+                continue;
+            }
             dev.openTag(SUMO_TAG_FLOW).writeAttr(SUMO_ATTR_ID, prefix + toString(flowName++));
             dev.writeAttr(SUMO_ATTR_BEGIN, time2string(c->begin));
             dev.writeAttr(SUMO_ATTR_END, time2string(c->end));
             if (!asProbability) {
                 dev.writeAttr(SUMO_ATTR_NUMBER, int(c->vehicleNumber));
             } else {
-                const double probability = float(c->vehicleNumber) / STEPS2TIME(c->end - c->begin);
                 if (probability > 1) {
                     WRITE_WARNING("Flow density of " + toString(probability) + " vehicles per second, cannot be represented with a simple probability. Falling back to even spacing.");
                     dev.writeAttr(SUMO_ATTR_NUMBER, int(c->vehicleNumber));