The closest parking garage is the Sixth Street Garage, located at 1201 E 6 Street. You can access the garage either by turning directly from Sixth Street or Lowell Street.
With the opening of the streetcar service, a printable map showing the location of the Tree-Ring Lab in relation to the nearest stop may be of interest.
Important Road Closure Information:
A construction fence will block both lanes on Lowell Street between May 19 and August 1, 2014. If you are visiting the Tree-Ring Lab, approach from either the driveway just east of the parking garage entrance on 6th Street (to the south), or from 4th Street leading to N. Santa Rita Avenue (to the north). The only exit is through Santa Rita Avenue. The map below shows two markers: to the east is the Bannister Building, to the west is the area of the road closure (zoom in [+] to see the detail).