Mightygoose's Compendium of Interchanges: The Reference Guide

[mightygoose]

INTRODUCTION

This is the read only reference guide that is being generated from my compendium of interchanges thread in the other projects board, this is meant to be reference material for relatively experienced users along to the same tune as Nardo's thoughts on railways....

please post any questions/comments in the other thread [linkie]



CONTENTS

PAGE ONE:

PART ONE:HIGHWAY ONSLOPE AND AN INTRODUCTION TO TRAFFIC

[mightygoose]

A wonderful tutorial not has just been uploaded detailing the construction of an underhighway roundabout. my version from a while back can be seen here.



But that is far from all that can be done with the elevated highway pieces and underpass interchanges.



Now currently this isn't possible with the AVE roundabout, but it does show off some NAM textures you may not have seen.
It was constructed by setting the terrain as if to make an AVE roundabout under highway but instead draw out the 4x4 road square. next diagonally draw in the avenue, the OWR's must be drawn from the road corner not into it. this means on one of the streches you will need to change the direction to match the other. (the offramps here are out of shot although access is restricted to the W>E carriageway only).



This is a different type of restricted access. this junction limits access only to and from the East. (fantastic for putting near the edge of a tile, as it forces out of tile commuters to use a larger portion of the highway, freeing up other roads for local traffic). At the end of the day interchanges aren't primarily there to look good. they are there to serve as an efficient and quick means of transferring traffic from one carriageway to another.



this junction at first looks like it has a redundant loop of OWR.(although not connected to the highway directly that parallel road becomes a feeder on the East side of the avenue and later connects). The reason for that loop is as follows:



If you consider the traffic signal cycle of the encircled junction. you can see that with the added loop of OWR bypassing the main junction the blue traffic arrow does not ever need to stop. the small secondary junction is OWR Westbound and road Eastbound, so no lights are required. On the main junctions the implications are this, you only have to have a two step signal cycle instead of a three step without the side road. This would allow alot more traffic to pass through the junction on any given day, reducing congestion and serving its purpose efficiently.



That is why unless the avenue is very quiet(if its that quiet you shouldnt have an avenue ) you will never see this in real life. the traffic lights creat pinch points that greatly reduce overall capacity.



where space allows a larger junction without the need for traffic lights should be used. keeping capacity and average traffic speed higher.

In fact i would say there are three Questions that you can ask yourself whenever you make an interchange.

1. How much space do you have? - use all available space but don't bulldoze existing buildings unless absolutely necessary, try to figure out a
                                               solution that fits in the existing space.

2. Who is going to use this junction? - where is you primary source of traffic, what is its destination. that route must have priority.

3. Do you need traffic lights? - they slow things down and create pinchpoints.