It might be significant that the study was on distance runners (though it's not clear what they mean by that). Road running definitely requires a lot more situ

It might be significant that the study was on distance runners (though it's not clear what they mean by that). Road running definitely requires a lot more situational awareness and decision making than track running. Uneven roads or sidewalks require instant reaction, especiall with snow/ice in winter. Cars, bikes, walkers, dogs, etc. can come from all directions and must be accounted for. Following a route and pacing for uphills/downhills also requires at least a little bit of thought. Trail running is even more challenging in some of these areas, though less in others. Running around a track is comparatively simple. It would be interesting to see how much - if any - of these effects exist for that kind of running.