## 2 Materials and Methods
### Testing
#### 2.4.2 Quantitative Tests  
The results of these qualitative tests were useful to modify the prototype design and the realized prototype itself. Once the new prototype will be ready, it will be equipped with accelerometers, potentiometers, and GPS, while the carriers will be equipped with a wearable metabolic system to perform quantitative tests of passenger comfort, dynamical behavior of the wheelchair and to measure carrier physical effort and performance. These quantitative tests will have three different purposes: (i) to verify the physical effort of the carriers through the monitoring of their oxygen consumption during the transport activity; (ii) to verify the comfort of the passenger using sensors on the cycling structures and on the seat of the wheelchair; and (iii) to verify the performance of the wheelchair suspensions. To ensure comparability of results, the same maneuvers and routes chosen for the qualitative tests will be repeated after equipping the wheelchair with the following instrumentation:  
* Triaxial accelerometer attached to the seat to check the comfort of the passenger. * Potentiometers mounted on the shock absorbers to check the suspension's shaking. * GPS. * Wearable metabolic system to check the oxygen consumption of guides (therefore their performance assessment and energy expended). The quantitative tests will be performed in two different vehicle configurations: (1) steerable handlebars, and (2) the handlebars rigidly connected to the frame, with a pivoting rear wheel. Figure 7: Example of field tests: (**a**) single step test; (**b**) flat path on grass; (**c**) grass track with ups and downs; (**d**) downhill mountain track. The rating scale uses a range from 1 to 5, where 1 is the least satisfactory score and 5 is the most satisfactory (1 = very poor; 2 = poor; 3 = fair; 4 = good; 5 = very good). The two considered aspects were: the drivability (Table 3) and the balance (Table 4), differentiating between the rear and front positions. Before starting the test session, the three carriers were instructed about the evaluation grid and the purpose of the test and of the survey. Tables 3 and 4 present the scores of drivability and balance tests, respectively, as they are felt by the carriers, showing the collected data and their average value, for each maneuver. Figure 8 illustrates these results, plotting the average values obtained in the nine different maneuvers, considering the front and rear positions. Looking at Figure 8, it is possible to observe that: (i) in the single step ( maneuver 1), there are very good levels of drivability and balance, both in the front and rear positions; (ii) in the long curve ( maneuver 2), drivability and balance are both very good in the front position and they are both good in the rear position; (iii) in the tight curve ( maneuver 3), the front balance is good, the front drivability is quite good, the rear drivability is fair, and the rear balance is quite fair; (iv) in the flat path on grass ( maneuver 4), there are very good levels of drivability and balance, in both the front and rear positions; (v) in the grass track with ups and downs ( maneuver 5), drivability and balance are both good in the front position and they are both fair in the rear position; (vi) in the uphill mountain track ( maneuver 6), drivability and balance are both fair in the front position and they are both quite fair in the rear position; (vii) in the downhill mountain track ( maneuver 7), balance is fair in the front position and is quite poor in the rear position, drivability is quite fair in the front position and is quite poor in the rear position; (viii) in the uphill hairpin bend ( maneuver 8), drivability is poor both in the front and rear position, balance is poor in the front position and it is very poor in the rear position; (ix) in the downhill hairpin bend ( maneuver 9), drivability is quite poor in the front position and very poor in the rear position, balance is very poor in both the front and rear positions.