"The most fundamental need in a bicycling network is low-stress connectivity, that is, providing routes between people’s origins and destinations that do not require cyclists to use links that exceed their tolerance for traffic stress, and that do not involve an undue level of detour. Evaluating network connectivity therefore requires both a set of criteria for tolerable levels of traffic stress and measures of connectivity appropriate to a bikeway network."

Sounds interesting! Especially that "tolerance for traffic stress" part.