**4. Conclusions**

This study demonstrates that the longitudinal characteristics of a trailer model have an essential influence on the *SRT* factor calculation. In this case, the *SRT* factor is approximately 38% lower than the previously reported standard value. This value is very close to that reported by Winkler [20] (i.e. 40%), which suggests that the proposed model provides consistent results [32].

This model also shows that the change in the lateral separation between the springs (*b*) plays an important role, and thus it should be considered in the design and construction of trailers. Greater lateral separation between the springs will increase the trailer model stability [32].

We also found that the parameters of the road, such as the bank angle and the longitudinal slope angle, can affect vehicle stability. This situation is closer to the actual problem: when the road is not planar, the lateral and the longitudinal load transfer play an important role in reducing the stability. On the other hand, this provides a very important warning, because some simplifications carried out when estimating the *SRT* factor can lead to a considerably higher stability value. This is a point of concern, leading to the perception that our roads are safer than they really are [32].

In the worst-case scenario, the trailer model, for a downhill corner with a bank angle of 0%, the longitudinal slope of the road of 8%, and a trailer/trailer angle of 20° can reduce the *SRT* factor of the model by 59.6%, using *0.4511 g* as a reference [32].

*Static rollover threshold (SRT) of the trailer model with trailer/trailer angle.*

**Slope angle (***φ***)-(%) Uphill corners Downhill corners**

 0 0.240 0.223 0.214 0.208 0.202 0.198 0.194 0.190 0.186 2 0.261 0.245 0.235 0.228 0.223 0.218 0.214 0.210 0.206 4 0.283 0.265 0.256 0.249 0.244 0.239 0.234 0.230 0.226 6 0.305 0.286 0.277 0.270 0.265 0.260 0.256 0.252 0.248 8 0.327 0.308 0.299 0.292 0.285 0.281 0.276 0.272 0.268 10 0.350 0.330 0.320 0.313 0.307 0.303 0.298 0.294 0.290 0 0.241 0.223 0.214 0.207 0.202 0.197 0.193 0.189 0.185 2 0.262 0.245 0.234 0.227 0.222 0.217 0.213 0.209 0.205 4 0.283 0.265 0.256 0.249 0.243 0.239 0.233 0.229 0.225 6 0.306 0.286 0.276 0.270 0.264 0.259 0.255 0.251 0.247 8 0.328 0.308 0.298 0.291 0.285 0.280 0.276 0.271 0.267 10 0.351 0.330 0.319 0.312 0.307 0.302 0.297 0.293 0.288 0 0.241 0.222 0.212 0.206 0.200 0.195 0.191 0.187 0.182 2 0.262 0.244 0.233 0.226 0.220 0.216 0.211 0.207 0.203 4 0.283 0.264 0.254 0.247 0.242 0.236 0.232 0.227 0.224 6 0.306 0.285 0.275 0.268 0.262 0.257 0.253 0.249 0.245 8 0.328 0.307 0.297 0.290 0.283 0.278 0.274 0.270 0.265 10 0.351 0.329 0.318 0.311 0.305 0.300 0.295 0.291 0.286

**86420 2468**

**Trailer/trailer angle (***ψ***)-(°)**

**Figure 34.**

**Table 6.**

**156**

**Bank angle (***ϕ***)-(%)**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

*(a) Lateral* CG *location. (b) Vertical* CG *location.*

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

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