Sub-problem 1c: Analysis of the Eastbound Freeway Section

You can compute the LOS by hand, but most software packages won’t let you do a single lane analysis directly. So you need to do a work-around. To begin, you can assume a volume of 1,620 passenger cars per hour and a two-lane facility. That yields a LOS of B and a density of 16.4 pcpmpl. So the truck climbing lane, if it’s used just by the trucks, operates adequately (see Dataset 7).

Next we need to check the remaining two lanes to see how they would operate if no trucks were present. The cars are 95% of the traffic stream, which means a volume of 3,080 veh/hour. On two lanes, with 0% trucks, that yields a per lane flow rate of 1,711 pcphpl, a density of 31.1 pcpmpl, and a LOS of D. The average passenger car speed is 55 mph (see Dataset 8).

Now let's consider the results of this hypothetical scenario. If we assume all three lanes are used by all the traffic, we get a density of 26.2 pcpmpl. If we separate the trucks into the truck climbing lane, we get 16.4 pcpmpl for the truck climbing lane and 31.1 pcpmpl for the remaining two auto-only lanes. These results suggest that trying to enforce exclusive use by trucks of the truck-climbing lane wouldn’t be a good idea.