--- a/python/traffic_engineering.py	Fri Jan 14 19:49:20 2011 -0500
+++ b/python/traffic_engineering.py	Mon Jan 17 16:46:48 2011 -0500
@@ -1,10 +1,69 @@
 #! /usr/bin/env python
-''' Traffic Engineering Tools.'''
+''' Traffic Engineering Tools and Examples'''
 
 from math import ceil
 
 __metaclass__ = type
 
+
+#########################
+# fundamental diagram
+#########################
+
+class FundamentalDiagram:
+    ''' '''
+    def __init__(self, name):
+        self.name = name
+
+    def q(self, k):
+        return k*self.v(k)
+
+    @staticmethod
+    def meanHeadway(k):
+        return 1/k
+    
+    @staticmethod
+    def meanSpacing(q):
+        return 1/q
+
+    def plotVK(self, language='fr', units={}):
+        from numpy import arange
+        from matplotlib.pyplot import figure,plot,xlabel,ylabel
+        densities = [k for k in arange(1, self.kj+1)]
+        figure()
+        plot(densities, [self.v(k) for k in densities])
+        xlabel('Densite (veh/km)') # todo other languages and adapt to units
+        ylabel('Vitesse (km/h)')
+
+    def plotQK(self, language='fr', units={}):
+        from numpy import arange
+        from matplotlib.pyplot import figure,plot,xlabel,ylabel
+        densities = [k for k in arange(1, self.kj+1)]
+        figure()
+        plot(densities, [self.q(k) for k in densities])
+        xlabel('Densite (veh/km)') # todo other languages and adapt to units
+        ylabel('Debit (km/h)')
+
+class GreenbergFD(FundamentalDiagram):
+    '''Speed is the logarithm of density'''
+    def __init__(self, vc, kj):
+        FundamentalDiagram.__init__(self,'Greenberg')
+        self.vc=vc
+        self.kj=kj
+    
+    def v(self,k):
+        from numpy import log
+        return self.vc*log(self.kj/k)
+
+    def criticalDensity(self): 
+        from numpy import e
+        self.kc = self.kj/e
+        return self.kc
+
+    def capacity(self):
+        self.qmax = self.kc*self.vc
+        return self.qmax
+
 #########################
 # traffic signals
 #########################