Over at City Commentary, a brief dissection of heuristics:
Five "Old Rules of Thumb"
- We should have a high level of service
- Wider streets are safer
- "Enough" off-street parking for every use
- Car trips are generated by every land use
- Hierarchy of streets
Four "New Rules of Thumb"
- Closer is better
- Slower is safer
- Sharing is efficient
- Design for accessibility not mobility