When I first drew maps for the MNPL about five years ago (I had just started to use Qgis but I can't really put a date on it) the NZMS1 maps for the area between Waitotara and Normanby suggested that three bridges around Waitotara and Patea were combined bridges, used by both road and rail traffic. Two in particular, Bridge 37 and Bridge 41, respectively east and west of Patea were explictly labelled as such.
In the course of redrawing these maps I have looked at the information for these bridges again to see if there is any more support for these suggestions. However, I have not been able to find anything that sustains these ideas and have concluded that it is not very likely at this stage that any of these three bridges were designed or used for road traffic as well as their primary rail usage.
If the bridges had been used for both types of traffic there would have been more information available about it because it should have been described in either railway or road documentation for the area, but no such documentation has yet been discovered, whereas other documentation tends to spell against these suggestions.
Here are maps of all three bridges.
Bridge 34 crosses the Waitotara River just west of Waitotara Station at the 78 km peg. A key factor against it being a combined bridge at any time in its life is it being so far from the Waitotara township. It would have been an inconvenient detour from the town to have reached this bridge. On the other hand it is close to the railway station and also close to another road bridge (Limeworks Bridge). At the moment there is nothing to show that the road layout has ever been anything other than what it is today. It appears the abutments of the previous bridge show it was just upstream of the current structure.
Bridge 37 crosses the Whenuakura River just east of Patea. On the one hand, there are overbridges on either side of this one, which would have suited the idea that a main road was sharing the bridge crossing. But on the other hand, in the aerial photography I was able to access, the road that approached on each side was no more than a dirt track, and today is nowhere to be seen. The highway crosses this river a considerable distance upstream. As we do know from previous posts recently, this bridge was severely damaged in flooding in 1922, and was completely replaced in 1930. The photos of the replacement show it was incapable of carrying road traffic. The original probably never did either. Again all I can document here is the location of the previous bridge. The road that did exist was most likely never anything more than a track formed to bring in materials for the new bridge construction in 1930 and any other maintenance needed since then.
Bridge 41 crosses the Patea River just west of Patea. We can state with absolute certainty that the Patea River was bridged for road traffic at Bedford St in the 1870s, the current structure incorporating Bridge 40 being a more modern replacement. There was therefore no compelling reason to need a road being able to cross at this location, which would have been pretty inconvenient for the people living in the township.