The Brooklyn suspension bridge in New York opened in 1883 and the Golden Gate suspension bridge in San Francisco opened in 1937. Both are still standing and daily handling huge volumes of traffic, considerably more than originally estimated.

The Forth Bridge, which opened in 1964 with a life expectation of 120 years, is now falling apart, cables snapping or unravelling. This is caused, we are told, by corrosion. Is this due to faulty workmanship or lack of supervision by the designers and consulting engineers?

The solution is to build a new bridge at a cost of £4.5bn. The Golden Gate, has a span of 4200ft, the Forth 3298ft. The GG has withstood earthquakes, winds in excess of 100mph, corrosive effects of the Pacific Ocean and 74 years on from its opening is still going strong. The Forth Bridge cost £11.5m to build; surely with the technology now available the cables can be repaired and sealed to prevent further climatic damage at a considerably lower cost than £4.5bn. And what would we do with the old one? Leave it as a monument to our engineering ineptitude or, at more expense to the taxpayer, dismantle it? Our climate is really no better or worse than California. That eliminates our experts' claims that all of the problems associated with the Forth Bridge are due to our climate.

Edward M Robertson, Muirshield House, Loganswell, East Renfrewshire.

We may look back upon 2007 as a year dominated by two icons of twentieth-century transport policy. The new Forth crossing and the M74 extension are the most expensive public projects ever promoted in Scotland. Yet the only serious doubt in their business case seems to be whether their exorbitant cost will continue to escalate over short periods of time.

Is it only the armchair pundits on The Herald letters page who can see through the paradox of promoting the endless and outdated policy of "just one more road". Your editorial (December 20) acknowledged the economic need for a new Forth crossing but also, bravely and refreshingly, challenged it. Could the tide be turning against the economic policy, where the wellbeing of the regional economy is more important than the health of its residents?

Beyond the cost, do we need yet more consultants to answer the common-sense questions? Perhaps the most pressing question is how Edinburgh will cope with a doubling of traffic from a new Forth Bridge.

Dr Stuart Nisbet, 15 Victoria Crescent, Glasgow.