# HG changeset patch
# User Nicolas Saunier <nicolas.saunier@polymtl.ca>
# Date 1398310552 14400
# Node ID 850ed17c7b2f77bfa65f3e0a92fd0e991c722806
# Parent  30fb60428e098d9bada2f9fb2494e46bc432f332
added some computation of delay

diff -r 30fb60428e09 -r 850ed17c7b2f python/traffic_engineering.py
--- a/python/traffic_engineering.py	Wed Apr 23 16:20:40 2014 -0400
+++ b/python/traffic_engineering.py	Wed Apr 23 23:35:52 2014 -0400
@@ -266,6 +266,15 @@
     '''Computes the uniform delay'''
     return 0.5*cycleLength*(1-float(effectiveGreen)/cycleLength)/(1-float(effectiveGreen*saturationDegree)/cycleLength)
 
+def overflowDelay(T, X, c, k=0.5, I=1):
+    '''Computes the overflow delay (HCM)
+    T in hours
+    c capacity of the lane group
+    k default for fixed time signal
+    I=1 for isolated intersection (Poisson arrival)'''
+    from math import sqrt
+    return 900*T*(X - 1 + sqrt((X - 1)**2 + 8*k*I*X/(c*T)))
+
 #########################
 # misc
 #########################