With experimental traffic data from a 4-mi (6.44-km) long congested road, it is shown that traffic delays and vehicle accumulations between any two generic observers located inside the road section can be predicted quite accurately from the traffic counts measured at the extremes of the section. Predictions can be made with a streamlined version of the kinematic wave theory that does not rely on ambiguous traffic stream characteristics such as density. The predictions were found not to require recalibration on the day of the experiment and to work well despite what appeared to be location-specific driver behavior.