It would be misleading to say Manhattan's newest crosstown bike lanes are unsafe, because that statement would imply that the lanes exist in any recognizable form.
The temporary protected bike lane on Smith Street in Downtown Brooklyn is an unmitigated (well, almost entirely unmitigated*) success — a quick solution to a long-dangerous gap in the bike network that was undertaken efficiently by a strapped Department of Transportation.
The Department of Transportation has not maintained its own temporary protected bike lane at the notoriously dangerous Second Avenue gap near the Queens Midtown Tunnel in Manhattan, forcing cyclists to ride with drivers racing to turn left into the tunnel.