P.J. Donnelly writes from Boyds, Md.: "At one time, I thought you were one of the few people in this area who had a clear and practical mind. Since your article about truck drivers on Thursday, 24 May 79, I had to revise my thinking.

"Don't you think you might be setting up a traffic hazard when you slow down to 40 mph? When I drive, I keep eyes front and look accasionally at rear view mirror. If I notice a car or truck coming up behind me at a fast pace, I always yield the right of way, even if I am going 55."

My clear and practical mind does not understand how one yields the right of way to a truck or car that is approaching rapidly from the rear.

On way would be to separate my car from the other fellow's by going even faster than he's going. It would merely substitute one danger from another.

Another alternative would be for me to move from the slow lane to the fast lane so that a speeding truck could pass me in the slow lane. This also strikes me as a poor solution.

The only other course I can think of is the one I described on May 24. When I am going 55 miles an hour and it appears a truck is going to come right up my tailpipe anyhow, I first try to get him to drop back by turning on my four-way flashers. If that doesn't work, "I gently begin to decelerate - first to 50, then to 45" or even to 40, until the trucker gets disgusted, moves to the fast lane and passes me.

If this creates a traffic hazard, I disclaim blame for it. I blame the driver who thinks his views on speed should take precedence over community views or rules.

When a speeder approaches from behind, yielding the right of way to him is easier said than done.

HISTORY REVISITED

On Tuesday, I noted that most Democrats elected president since the Civil War have served more than four years. This reminded Donald Brenke of the "20-year jinx" that may be worrying several presidential aspirants these days.

William Henry Harrison was elected president in 1840. He died in office after serving for one month.

Ever since then, the presidents elected at 20 year intervals have died in office: Lincoln, who was elected in 1860, Garfield in 1880, McKinley in 1900, Harding in 1920, Roosevelt in 1940 and Kennedy in 1960. "If this trend is to continue," Brenke comments, "the vice-presidency is the office to run for in 1980."

Well, I suppose that's right. Something that happens in 1840 and again in 1860 and again in 1880 might be termed a coincidence. Add 1900 and it becomes a curious coincidence. By 1920 it might be an ominous coincidence, and in 1940 a subject for statistical calculation. By the time John F. Kennedy was shot, the subject had become gruesome. One felt like a ghoul in discussing it.

Several disclaimers should be noted:

Eight presidents have died in office. Only seven of them were involved in the 20-year jinx. Zachary Taylor (elected in 1848) died in 1850.

Four of the eight who died in office were assassinated - Lincoln, Garfield, McKinley and Kennedy. The other four died of natural causes.

Two of the seven presidents on the 20-year list did not die during the terms that made them eligible for the so-called jinx. Lincoln survived the term to which he was elected in 1860. He died in '65, during his second term. FDR survived the term to which he was elected in 1940. He died in '45, during his fourth term.

If you show me statistics that reveal a higher death rate for people who followed one life style than for people who follow an opposite course, I am impressed. I might not understand why things like drinking, smoking, drugs, hypertension or unbalanced diets hasten death, but I would have to be impressed by the possibility that a causal relationship exists.

However, I see nothing in the 20-year cycle of deaths that could be causal, and I keep telling myself that I don't believe in jinxes. If I were a candidate, I would not be deterred from running.

This certainly marks me as a brave man, doesn't it? The jinx doesn't frighten me, mostly because there is no danger of it affecting me.

TGIF DEPT.

Deadpan dispatch from Don Epperson: "Most economists can't predict exactly when a business slowdown will occur, but I can: On most days, it occurs at 4:15, on Fridays at 3:30."

THAT'LL BE THE DAY!

Changing Times comments: "Being human, auto manufacturers make mistakes. But being human, they never make the mistake of putting an Olds engine in a Chevy."