With a rail station in the area of Hancock Center, there would be access to UT on existing shuttle route RR with little if any modification. More importantly, the City of Austin is considering this area as a terminus for urban rail. Potential locations for the new metro station include:
The I-35 underpass. With required pedestrian improvements, immediate access to Hancock Center and routes 37 and 320 on I-35 frontage road. This would not be ideal for RR unless it were put on a big loop like the current 338. Urban rail would be walking distance but not likely convenient. With modification of the turn-around on the southern edge, route 350 can be brought in from Airport Blvd. With pedestrian improvements to the northern edge, access to Airport Blvd.
Property just east of I-35. With development of a facility here, several routes could be brought in along the underpass just north of 41st, but this is even less ideal for RR and highly impractical for urban rail. Otherwise, this would be the best location for an off-street transit center, in my estimation, with potential for paid parking under I-35.
Land between Clarkson Ave and Airport Blvd at Ellingson Lane (or from 44th to 45th). Access to routes 338 and existing RR alignment. Reasonable access to routes 350 and 10 or closer with realignment. Farther from Hancock Center and routes on I-35 though these are within walking distance along Clarkson. Nearby properties are all residences, but apart from that, this may be the best location in my opinion. I'd wonder if those residences could be rezoned.
Land between Clarkson Ave and Airport Blvd from Red River to 51st. Access to route 10 and possibly RR with extension. Unknown potential for crosstown bus route along 51st. There's the opportunity for a rail crossing and traffic light at 50th to ease congestion at 51st. Urban rail would be most easily accommodated here.