The average road user will tolerate a certain level of
congestion and delay before becoming frustrated or annoyed
or attempting unsafe driving manoeuvers.
To address the issue of acceptable degrees of congestion,
the level of service concept has been developed. The various
levels have been subjectively determined and quantatively described. (1)
From various USA references, the Level of Service (LOS) of a road is categorized from "A" to "E", where "A" is excellent and "E" is terrible. On the internet examples of these definitions can be found. (2)
Simply put, from the individual's side, everyone wants to get to their destinations faster. From the society viewpoint, we need efficient roads to grow the economy. More and more today we also need to avoid wasteful use of fuel on inefficient roads. For those reasons we all want to see road congestion cleared. However, to provide improved level of service (LOS) money needs to be spent with that as an objective and certain TRADE-OFFS need to be made.
The buzzwords "context sensitive design" and "multi-criteria matrix appraisal framework" are also used alongside LOS in both SANRAL and ASSHTO's geometric design guidelines to describe this tradeoff process, which is intended to take all factors into consideration before any decisions are made.
While SANRAL's Geometric Design Guidelines is a very comprehensive document, it is also highly theoretical with long passages taken from the AASHTO big daddy, and for the designer at the coal face I dont believe it is of much use when the pressure is on. A subtlety like LOS will not be part of the decisions taken unless it is a policy requirement from a higher level, like DOT, and it was clearly absent in the NMBM BRT planning