Highway markings define the junction point to occur at this sign. Starting from this sign, lanes are treated as separate exit offramps through the tunnel and until their departure from the freeway.

Previously this was modeled as a single 3-lane highway over this distance with no lane changes allowed, but this caused some navigation software to interpret the actual junction point as being further along the highway, after the tunnel. Splitting the highway to three roadways at the marked junction point appears to be the strategy visible in other mapping platforms (see: public Google Maps data for this region), and I've updated the road data here accordingly.