# Methodology to Assess Sustainable Mobility in LATAM Cities
## 3 Results
### Key Performance Indicators
#### 3.2.3 Environmental Impact  
_Vehicle Energy consumption:_ For the case study, measurements through the On-Board Diagnostic (OBD) port and a Global Positioning System (GPS) were carried out on 14 vehicles for 16 months between February of 2019 and June of 2020, obtaining a total of 2.09 million of records. For data quality analysis, trips with more than 5% of missing data were neglected. In our test vehicles, the volumetric fuel consumption rate (\(\dot{V}_{f}\)), expressed in L/s, was reported by the Engine Control Unit (ECU) through the OBD port. It was estimated through Equation (5). It uses data from the mass airflow sensor (_MAF_), the corresponding fuel stoichiometric air-fuel ratio (_AFR_), and the region of study declared fuel density (\(\gamma\)), which is 870 g/L for Saltillo [72]. This technique has been previously validated with an error lower than 6% [73]. \[\dot{V}_{f}=\frac{MAF}{AFR\cdot\gamma} \tag{5}\]  
Figure 9 details the Specific Fuel Consumption (_SFC_) obtained of each vehicle category measured, expressed as quartiles. The horizontal line marks the median value, while the whiskers indicate variability outside the upper and lower quartiles. When considering the fuel consumption of cargo freight, the best way to analyze trucking efficiency is to determine the SFC per ton of freight weight (_SFC_*) [74]. Therefore, to include the cargo freight category into the analysis, this metric is used for every category measured. Figure 9 shows that cargo vehicles are the most energy-efficient. _Vehicles' emissions_: Aiming to evaluate Saltillo's vehicle emissions, the latest local anthropogenic emissions inventory was retrieved from the Secretariat of Environment and Natural Resources [75]. The methodology used in the emissions inventory in Saltillo is detailed within the guide for the preparation and use of emissions inventories prepared by the Mexican's National Institute of Ecology and Secretary of the Environment and Natural Resources, in collaboration with the Western Governors Association [76]. In Saltillo, the vehicles are the primary source of CO, the secondary source of VOCs and PM, and the tertiary source of NOx (Table 6). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Year** & **Strategy** & **Reference** \\ \hline
2004 & Improved buses, cards, created routes, surveyed & \\  & origin-destination. & \\
2013 & IMPLAN establishment & \\
2015 & East Area Public Transport Analysis—Boulevard Carranza & \\
2015 & Urban mobility indicator system & [56] \\
2015 & Recommendations guide for the improvement of the bike & \\
2015 & path segment: Government Center—Distributor Vial “El & [69] \\  & Sariape” & \\
2015 & Recommendations to the project denominated: “update & \\  & technology of parking meters & [70] \\
2016 & Analysis of urban mobility in the Saltillo historical center & [68] \\
2017 & Design guide for pedestrian infrastructure. & [71] \\
2019 & Study of vehicular emissions in the city of Saltillo using & \\  & the remote sensing technique & [58] \\
2020 & Proposal for reorganizing mobility in the historic center & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Timeline of the mobility strategies implemented in Saltillo. In addition, the results from the 2019 RSD monitoring campaign for on-road emissions were also included in this analysis. This RSD monitoring campaign was previously described in Section 3.2.1. Aiming to avoid atypical data, as suggested by Mexican RSD standards, only results from vehicles driven under vehicle speeds between 1 and 35 mph (\(\sim\)1.6 to 55 km/h), positive accelerations between \(-\)2.8 and 4 mph/s (\(\sim\)\(-\)1.2 and 1.8 m/s\({}^{2}\)), and with _VSP_ values between 3 and 20 kW/metric-Ton were considered [48]. _VSP_ is the power demanded by the engine. _VSP_, expressed in kW/Metric Ton, was obtained with Equation (6) using typical values [77]. In this equation \(v\) and _vw_ are the vehicle speed and wind speed respectively, both expressed in m/s, \(m\) is the road grade expressed as a percentage, and \(a\) is vehicle acceleration in m/s\({}^{2}\).