Tips for routing with tiger file

[Tim Bowden]

On Thu, 2007-07-05 at 05:21 +0000, Kurt Kuo wrote:
> Dear list,
> Here may not be the right place to post this question. However, I understand 
> that mapserver users come from different fields. There must be some experts 
> who are able to give me some advices. Thanks in advance.
> My question is how to use tiger file for routing purpose. As my 
> understanding, routing needs the length of every line between source and 
> target nodes. It seems that the tiger file does not have this information. I 
> really appreciate if someone can provide some advices, tips, or references 
> in order to achieve this matter. Thanks again.
> 

Tiger data is not so good for routing; It does not contain any data
about one way streets or intersection controls (i.e. no left turn etc).
Some intersections shown on tiger data are not even an accurate
reflection of what's on the ground; Things like freeway overpasses that
don't physically intersect with the road being crossed appear as
intersections in the tiger set.  As far as I am aware, for accurate
routing you will need to purchase a commercial data set.  Remember that
tiger was initiated for census work, and the data has limitations when
you try and bend it to other uses.

HTH,
Tim Bowden