The results indicate that the
higher CO2 emissions on uphill sections are not offset by the lower emission rates on downhill sections. The discrepancy over
the combined sections tends to rise as the road grade coefficient applied in the PHEM modelling increases. The magnitude of
the increase in emission is greatest where the average road grades of the two sections of opposing traffic flow are steepest.
It should be noted that the traffic conditions in the road sections that make up the combined pairs can be quite different
for each direction of traffic flow, as traffic control measures and traffic volume can cause different levels of congestion,
resulting in a wide range of CO2 emission values in each section (as illustrated in Fig. 4). However the results in Fig. 7 present
the calculated emission from real-world speed profiles recorded throughout the day, and thus these combined emissions
should reflect the likely range of CO2 emission for the test vehicle on these real-world road segments.