For those vehicles which complete the trip from the starting road to the ending road, we define the timestamp it reaches the destination (enter the last road segment) as $t_e$. Then the travel time is defined as the time difference between its starting time $t_s$ and ending time $t_e$ and it is calculated by:
$$ \tau = t_e - t_s $$As for the rest of the vehicles which have not reached the destination when the system time is over at timestamp $T_{max}$, their travel time is calculated as:
$$ \tau = T_{max} - t_s $$Then for one test scenario, the metric Travel Time is calculated as the average travel time of all vehicles where $n$ is the number of vehicles.:
$$ T = \sum_i\tau_i/n $$Obviously, the objective of this problem is to seek a better signal timing plan to minimize the average travel time $T$.
For each test scenario $i$, we have a baseline travel time $b_i$, then the score of the i-th scenario is computed as the relative improvement over the baseline results: $$ score_i = \frac{b_i-T_i}{b_i} $$
The baseline result is based on the result from SOTL algorithm, which is provided in the sample code.
For $n$ different scenarios, the overall score is: $$ overall\ score = \sum_i score_i/n $$