Changes between Version 1 and Version 2 of HighwayModel

Timestamp:

10/06/2017 07:28:09 AM (9 years ago)

Author:

jdalbey

Comment:

Initial release

HighwayModel

@@ -3 +3 @@
 First draft of data structure for representing a highway network that can model traffic congestion.
 
+[[Image(intersection_sketch.jpg)]]
+
+
+'''Highway''' (as shown in sketch) is a highway name and a list of LDS's (Lane Detector Stations).
+
+'''Intersection''' is a postmile number and a cross street identifier.
+
+'''Junction Map''' is a data structure to model highway intersections (junctions), 
+A map that associates highways to the cross streets that intersect them.
+
+
+'''Example Map'''
+
+Hwy 123: [(17, Hwy 456), (54, Hwy 789)][[BR]]
+
+Hwy 456: [(93, Hwy 123), (117, Hwy 10A)][[BR]]
+
+Hwy 789: [(22, Hwy 123)][[BR]]
+
+
+In the example Hwy 123 has two cross streets: Hwy 456 at postmile 17 and later at postmile 54 it crosses Hwy 789.
+
+
+== Simulating Congestion ==
+
+Alternative 1.  Every 30 seconds traverse the network from the incident origin point to find the next LDS that is unaffected, then change its state.
+Pro: Simple concept, needs only the data structures above.
+Con: In a very large network performance would be slow.
+
+Alternative 2.  Maintain a "state" that knows the current extent of congestion and can quickly identify next LDS to be changed.
+Pro: Better performance.
+Con: Additional data structures needed.
+
+Decision: We prefer alternative 1.  We don't expect out network to be large enough for performance to be a factor.  Even a list of thousands of LDS could be traversed in a second and we have 30 second intervals between ATMS updates.
+
+
+