AHTD has the plans for this bridge posted on the "historic bridges" page of their website. Those plans, consistent with the other comment and Street View, confirm that the Laney Bridge's west approach was originally built for the Martin Bridge, apparently in 1934; the sidewalks on each side of that approach were bolted on when the rest of the Laney Bridge was built in 1947. The concrete railings on the west approach match those in this site's photo of the Martin Bridge, taken in 1939; they change from concrete to metal (and the sidewalks move from outside to inside the railings) at the west end of the main spans, clearly the transition between the 1934 and 1947 structures.
Visited this bridge on 6 Sept '09. On the west approach to the Ben Laney Bridge there is a bronze plaque with date of 1934 - possibly from the Martin Bridge that was replaced. The approaches for this bridge also feature walkways or both sides. See attached photos.
Webmaster's note: The photos that were here have been incorporated into the main site.