You can go through the Lyttelton Road Tunnel on foot, by bike, or skateboard on Sunday 31 August, from 9.30am to 12.30pm. At the other end of the tunnel, there will be a market day in Lyttelton hosted by the Lyttelton Harbour Business Association. The library mobile van will be outside the Lyttelton Library, with storytelling for children.This occasion celebrates 50 years of the Tunnel, the opening of the new tunnel control building and national recognition for its engineering heritage. Read more: Triple celebration for Lyttelton Tunnel. NZ Transport Agency: Southern Region and Cycling in Christchurch.
Read the NZTA PDF with full details of how you get there and home etc.
On Monday 1 September at 7 pm Jack Smith, who was involved in the tunnel construction, will speak in the Lyttelton Library about his experiences and promote the book he has written as part of the Fletcher Construction history series, No job too hard.
The Lyttelton Road Tunnel opened 27 February 1964 creating a vital link between the city of Christchurch, New Zealand and its port Lyttelton. The tunnel complemented the long established Lyttelton Rail Tunnel. It is the longest road tunnel in New Zealand.
The Lyttelton Road Tunnel Administration Building at the Heathcote (Christchurch) end of the tunnel was designed by Christchurch architect Peter Beaven. The distinctive building was demolished in the aftermath of the Christchurch earthquakes.
NZTA reports the new $1.5 million tunnel control building, designed by Wellington-based Architecture Lab and built by local company Higgs Construction to 160 percent of the Building Code, signals a new era for the operation of the tunnel.
Christchurch City Libraries Blog 
More information about this at “Cycling in Chch”: http://cyclingchristchurch.co.nz/2014/08/03/bike-the-lyttelton-tunnel-sun-31st-august/
Thanks Glen, I will add a link to this into the blog post itself.