When I've used Dodger Stadium in the past, HR hitters tended to get closer to their numbers than in a negative 1B factor park with positive HR factors. My experience says that it does kill doubles and triples, which isn't surprising given the -4 and -3 hit factors, respectively. A negative 1B factor keeps overall hits lower, not just singles. In a park like Riverfront, there will be fewer overall hits because of a -2 1B factor but HR (+1 to each field) and doubles (+2 factor) will comprise a higher percentage of total hits. Since triples have a 0 factor in that park, their percentage of hits should be theoretically unchanged.