WELCOME the letters (May 15) from Dave Stewart, Dave Holladay, and Mark James, referring to my letter published on May 11. Proper discussion is exactly what the subject of traffic in cities needs: only that way will it be better understood, and it is hard to think of any subject that is less well understood, even by the so-called experts.

There is little in Dave Stewart's letter with which I would take issue, and he is absolutely right about the ''park-and-ride alternatives'', but (e) must be added to his conditions - namely that it is possible to park. Our local Blue Train car-park is absolutely full before 8am, and many others are the same.

I for one would be happy to see much of Byres Road in Glasgow pedestrianised, like the streets in the centre of the city, but, if the shops are not to die, alternative access must be provided. This is the job of the planners and politicians, but they have failed completely over many years, and now want us to pay for their incompetence!

There is one small point which needs to be corrected - I do pay my share for the upkeep of the city, through business rates which are rather heavier than council tax.

The first paragraph of Dave Holladay's letter reveals that he is not aware of the proper definition of ''efficiency'', which is ''the ratio of useful work to the total energy expended''. Because a car goes directly from A to B in the minimum time, virtually all its work is useful.

Public transport usually leaves from the wrong place, goes to the wrong place, and often takes three or four times as long to do it, at higher cost. It does not require a genius to work out that a car is far more efficient than public transport, and some 20 million car owners in Britain have done just that.

But the worst errors are in Mark James's letter. First, if he re-reads Mr Begg's letter he will see that it does not offer any solutions - what Begg offers is restrictions, not solutions, without making the necessary provisions to make them work.

Secondly, my statement that cars are six to eight times less polluting than 10 years ago is not an assumption: rather, it is the result of highly scientific Swedish tests on British cars, as he can see in the current issue of What Car? magazine.

Almost certainly, the main cause of the small drop in average mpg last year was traffic congestion: traffic congestion is the result of poor traffic organisation, not increased traffic flow.

It really is time for walking and cycling to be left out of this discussion - they are both excellent ways of keeping in shape, and enjoyable in decent weather, but they are not viable ways of commuting for most people.

Peter M Spinney,

Westerton Dean, Mugdock, Glasgow.

May 18.

GLASGOW City Council has recently launched two important initiatives: after lengthy public consultation, it has produced an environment strategy ''to provide a framework for the development of environmental policy in the context of Agenda 21'', and the public are asked to comment on the draft consultation paper, ''Keep Glasgow Moving''.

Both documents recognise the necessity to curb the use of the private car if issues of health, road safety, congestion, and climate change are to be addressed. So it is all the more disappointing to read (May 13) that the council is still determined to go ahead with the completion of the M74 through the South Side of this city, which would carve yet another vast swathe of tarmac through the Dear Green Place.

Many studies, including that of the Government's own advisers on trunk roads, have shown that building more roads increases traffic, and that jobs are as likely to flow out of the area as in. Instead of wasting #180m on an outdated motorway scheme, the same level of investment would be better spent on improving rail links for freight and passengers, and on providing priority routes for buses, cyclists, and pedestrians.

Sara E Barry,

Glasgow Group Co-ordinator,

Friends of the Earth, Glasgow,

13 Mirrlees Drive, Glasgow. May 15.