KLD established an early reputation for building exceptional traffic simulation models. As part of the FHWA Urban Traffic Control (UTCS) 1970s testbed in Washington DC, KLD created the UTCS-1 traffic simulation model to evaluate alternative traffic control policies and to provide relevant metrics (delay, stops, emissions). In later work building on this, KLD built the NETSIM and other models for FHWA. The NETSIM model was incorporated into FHWAs COSIM model as the surface street component of that model.
UTCS-1 and then NETSIM were microscopic traffic models that incorporated a set of fundamental building blocks of driver behavior car-following, lane changing, gap acceptance, acceleration by vehicle type, randomness in driver characteristics, interaction with pedestrians, and other elements. Each of these building blocks was calibrated. The use of discharge headways allowed lane and intersection capacity to be addressed directly. Over time, 2- and 3-dimensional displays of traffic movements were added features, as were time-space diagrams of traffic movement.
KLD also developed an enhanced version of NETSIM (designated as WATSIM) to serve local agencies, and used it in its assessment work. WATSIM was also marketed in Japan, and used extensively there.
Efficient layout of toll plazas were drawing attention, and KLD with the support of NYSERDA developed the GENTOPS model to build on the NETSIM/WATSIM family, to analyze operations at toll plazas with different geometries, number of toll lanes, traffic volume and composition, mixes of toll collection types (cash, ETC, mixed) and layout of toll lanes. The tool was used extensively in the northeast US, but had limited market penetration.
Concurrent with its work on modeling, KLD developed a number of algorithms for traffic signal optimization, including work on the 3rd generation of UTCS and later IMPOST.