

Traffic density doesn’t cause any problem, it is slow traffic anyway, especially last-mile localities. Maybe there are no local trains on his route.
The main concern with traffic density would be polluted air, which you’d breathe more of when cycling.
Well, population density does that, I guess! Not much to be done about it, even in other parts of India with population not as crazily dense as Mumbai.
Between that and avoidable traffic jams created by vehicles blocking intersections, cycling may be the fastest method but also needs breathing more polluted air. But the time overhead of public transport can’t be reduced with this population density. So … a rock and a hard place!