[postgis-users] Calculate driving distance in postgis

[K Kuo]

Hi List,
Does anyone have a better way to calculate driving distance in postgis?
I have a database which convert from tiger/line data. I have found that I 
can use distance_spheroid function to calculate distance between two points, 
which supposes to be the shortest distance instead of driving distance, am I 
correct? What I am thinking about is that I have to query out all nodes 
alone the route, calculate distances for each segment then add them up. I 
don't think this is a good approach. Any suggestion?
By the way, the tiger/line data contain fnode, tnode number for each line 
segment. How can I get the long/lati value from postgis.

Thank you very much.

Regards,

Kurt