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Knowledge Base Article:IMW135 
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How to make a ramp a corridor for query purposes.

Article created: Nov 12 2003, updated: Nov 12 2003

Background:  To be able to draw a corridor diagram for the length of a ramp.
Status:  Info - "how to" article
Keywords:  corridor,ramp,corridor diagram,diagram,cross streets,streets manager
Categories:   *Diagrams*

Explanation:
Since ramps have unique characteristics (mainly direction of travel), it is difficult to draw a diagram of the entire length of the ramp. For instance, a ramp may start N-S and curve to end up going W-E. Since the ramp itself has two different directions, it's hard to treat it as a corridor.

Solution:
First you must split up the ramp into two different sections, inserting a "dummy" street as the dividing cross street. As this picture shows, a normal ramp is curved. To create sections of this corridor, we must visualize the separation of it as the 90 degree angle which is drawn (using pink lines) with the dividing street called "Fake Street".
diagram illustrating a ramp

To apply this concept, follow these instructions:

  • Go to Utilities/Database/Streets Manager
  • Select the name of the ramp as the primary street
  • Select the first intersecting road of the ramp (ex: N/S Street) and select the "Direction to next" as W-E (as this picture shows, the pink line from N/S Street to Fake Street travels in the W-E direction).
  • Now you must create the street "Fake Street". On the right side of the streets manager utility there is a section called "Streets". Next to "Add", select "one".
  • Type in the street name "Fake Street", and select o.k.
  • Select o.k. to the message that the street was added.
  • When asked if this new Fake Street is a cross street of the primary street previously selected, select yes.
  • You will see that Fake Street has been added to the cross street list you are working on. Make sure it is positioned second in the list with a "direction to next" as N-S.
  • Now make sure the final street (which is the ending intersection of the ramp and the second street involved; here W/E Street) is listed with a "direction to next" as N-S.
  • Select Done to close the streets manager.
  • Now create a new diagram, selecting Intersection Corridor as the type of diagram.
  • Select the ramp as the primary street.
  • For the corridor from/to section, select the box w/ three dots to the right.
  • Be sure to select all streets listed as the cross street for this ramp (as defined in the streets manager).
  • Make sure all the calculations for crash counts at the bottom of this window are correct (we recommend leaving them all zero, individual situations may call for different calculations). Select o.k.
  • Now you may generate a diagram containing all crashes along a ramp that goes from one street to another.

The directions used in this example pertain to the picture shown. The actual directions that you may need to use could be different depending on the streets you are using.

It is important to mention that this process only works if the accidents are coded properly for Direction From Intersection. For example, in the above drawing, if the accident was not coded west of the N/S Street (going onto the ramp), then it would not show in the diagram called upon when generating a corridor diagram using all three streets: N/S Street, Fake Street, and W/E Street.
September 08, 2010 6:00AM

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