Access Points Access points are major driveways and side roads where significant traffic enters and/or leaves the two-lane highway within an analysis segment. Access points lower the free-flow speed (FFS) for the segment. By lowering the FFS, access points will also indirectly affect the average speed and the follower density. Residential driveways and other low-volume driveways and side roads (generally with average daily traffic below 20 vehicles per day) are generally not counted as access points.
Treatment of Terrain and Heavy Vehicles Unlike other facility analysis methodologies in the HCM, the two-lane highway analysis procedure works directly with traffic stream units of vehicles per hour, rather than passenger cars per hour. That is, passenger car equivalent (PCE) values are not utilized. This approach provides the ability to more accurately represent the performance measure relationships as a function of the more varying horizontal and vertical alignment often encountered on two-lane highways. Additionally, it simplifies the analysis methodology by removing the process of converting units from veh/h to pc/h. The two-lane highway analysis methodology therefore includes the percentage of heavy vehicles as an input to the performance measure estimation models.