This has happened to me once, in each of the last 2 races I did. The races were on roads with a fairly wide shoulder (4-6 ft.) I do not ride at the edge of the shoulder, but about six inches outside the white line. Shoulders tend to have more debris and the likelihood of a flat is higher. I was passed on the right by another rider. I believe I was staying to the right as I was right next to the white line and therefore the rider passing on the shoulder was not following the rules. What is staying to the right, the white line or the shoulder?
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"When I first had the opportunity to compete in triathlon, it was the chicks and their skimpy race clothing that drew me in. Everyone was so welcoming and the lifestyle so obviously narcissistic. I fed off of that vain energy. To me it is what the sport is all about."