I agree with you that increased speeds are not likely to be the “main reason,” as mentioned above. I cycle 12 miles per day on my daily bike commute to work in Mexico City so I was treated to a first-hand look at the Swine Flu scare unfolding. It strikes me that normally congestion in Mexico City causes intersections to be blocked by motor vehicles (morning, noon, and night) which reduces potential for fatal collisions. During the Swine Flu scare those intersections were open, resulting in more “Left Turn” and “Right Angle” collisions and therefore more fatalities.

Just my observations.

Kind regards,
Tom Bertulis
ITDP Mexico City