NO ETERNITY IN BRIDGES

Evening Post, Volume CIX, Issue 125, 29 May 1930, Page 8

NO ETERNITY IN BRIDGES

"Many of these so-called permanent bridges have become obsolete in less than ten or fifteen years." That statement by the California Division of Highways, since quoted with appreciation by the 'New Zealand Main Highways Board, gives a very direct angle of view into the complexities of New Zealand's bridge renewal question, dealt with in an article in yesterday's "Evening Post." Of what avail is it to "buildfor all time" (to build in stone, or in iron, or in the combination thereof called reinforced concrete) if you build your bridge in the wrong place, or of the wrong width, or on the wrong alignment, so that fast modern traffic will not (cannot)' use _it safely?* Such is'the question raised by modern road engineers, who see so many possible : factors of traffic change that in many cases they prefer wooden bridges, "the saving in first cost being more than enough to rebuild,at the end of thirty-five years." And if the bridge is obsolete for traffic in ten years, so much less the capital loss. The "permanent" bridge may defy time but cannot prevent change. New Zealand has known rivers that took short cuts and left their bridges high and dry and isolated.. Besides, presently we may be. flying over the bridges, and putting special taxes on aeroplanes in order to keep people on the roads.