If you work with transit data, you might want to take a look at the following blog post. Some great suggestions:
- Use services areas around transit stops instead of buffers around transit lines
- Incorporate frequency, like trips made per hour
- Consider travel time between places throughout the day
- Factor in transit frequency
- Incorporate demographic data to find what groups are underserved by transit or have a high level of need for better access to certain types of destinations
Check it out.