All things being equal except for the tandem team's higher combined weight (i.e., brake technology, skill level, road conditions), a tandem cannot stop in less distance than a single bike -- it's simple physics.

My "may or may not" comment relates to reality where all things aren't equal and where the biggest variable on stopping distance is reaction time, i.e., where the rider's experience, bike handling skills, judgement and paying attention all come into play. This is the wild card when you get large mixed skill groups on the road at the same time.

As a general rule, we will not let inexperienced cyclists knowingly ride in our tandem's draft nor will we ride on the back wheel of a squirelly rider or pace line that can't hold a steady pace (the slinky-effect). It's just too stressful to be fun. This is one of the reasons that I strongly encourage tandem teams looking to ride with other fast tandem teams to attend tandem rallies. This is the only place where you'll have a chance of finding enough tandem teams who are roughly able to ride at your same skill level who you can safely share pace lines, hill climbs and descents with given that the machines are all well matched relative to their inherent performance.

The only thing tandem teams will need to start being mindful of are the newer tandems being fitted with mechanical discs as their primary front or rear brake systems. While the various types of rim brakes (arch, cantilever and linear pull) all have very similar stopping characteristics under the same conditions the mechanical disc brake-equipped tandems will be able to out-brake (i.e., deccelerate faster and come to a stop in less distance) rim brake equipped tandems dramatically in wet conditions and even quite dramatically in dry conditions as well. The disc brakes also tend to be more difficult to "feather" for speed adjustments such as in pace lines vs the rim brakes (a little disc brake action goes a long way). Therefore, be sure that any time you are riding in a group of tandems where someone has disc brakes that y'all remind each other about the inherent difference in braking abilities. The last thing you want to have is the fastest ride on a dual-disc equipped road tandem initiating a panic stop during a 40mph descent with 10 rim-brake equipped tandems in tow.... It could get ugly if the disc-equipped tandem captain doesn't take the other tandem's braking limitations into consideration.