Highway 3A is the designation of two segments of highway in the southern part of British Columbia.
Castlegar-Nelson-Creston Highway
thumb|Cyclists along British Columbia Highway 3A near Kootenay Lake.
thumb|right|The "Big Orange Bridge" carries Highway 3A over the Kootenay Lake (West Arm) in Nelson.
This was the first segment of highway in British Columbia to receive the '3A' designation. It acquired this designation when the Crowsnest Highway was routed into the Kootenay Pass area in 1964. Originally, a ferry was used to route Highway 3A over the Columbia River near Castlegar, which was replaced by a bridge in 1967.
The long Kootenay section of Highway 3A begins at Castlegar, where it leaves Highway 3 and travels northeast to South Slocan, where Highway 6 merges onto Highway 3A. The two highways proceed east for to Nelson, where Highway 6 diverges south. northeast of Nelson, Highway 3A reaches Balfour, on the western shore of Kootenay Lake. A ferry takes Highway 3A across Kootenay Lake to Kootenay Bay. Highway 3A then follows the eastern shore of Kootenay Lake for south through Crawford Bay, Boswell, and Wynndel to Creston, where it rejoins Highway 3.
The 3A marker in Creston at the junction with the Kootenay pass route falsely advertises it as a northbound highway rather than a westbound highway although all other 3A markers properly describe it as west and eastbound just as the 3 main.
The Kootenay pass is prone to closures especially during avalanche season and when it is closed Highway 3A and the Kootenay Lake ferry once again becomes a vital link for all traffic on the Crowsnest highway which would otherwise completely cease to function. The ferry will operate on a 24h basis until the pass re opens.
Even when the pass is open and despite the pass route being shorter some Kootenay locals still personally prefer to drive the Kootenay Lake route rather than the Salmo Creston route viewing the ferry route as a safer option especially if the weather is bad or at risk of turning bad or if there are construction delays on the pass. It's possible for example for the entirety of 3A from Creston to Castlegar to be bare and dry while the pass is still covered in snow and ice. 3A is also a far easier bicycle route than the Kootenay pass. This combined with people who simply wish to experience a more relaxed drive means a significant minority of ferry users in a given week are using the ferry as part of a trip all the way to or from the coast just as it was used for before the pass route was built.