**4.2 Numerical results**

In **Table 1**, the travel times obtained during peak hour simulation after model calibration are shown as well as the RSME. **Table 2** shows the queue lengths obtained during peak hour simulation after model calibration are shown. Let us observe that with reference to the results displayed in **Table 2** regarding the simulation of the current scenario, the main critical points are identified on Via Caracciolo (see **Figure 3**, junctions 1 and 2 are along Via Caracciolo) and Galleria Vittoria, direction W-E. For these two roads it was possible to reconstruct (in the condition of full network loading) the mean maximum queue lengths for intervals of 900 seconds or 15 minutes that fluctuate between 200 and 300 m on Via Caracciolo and between 300 and 400 m on Galleria Vittoria W-E. In the same table the root mean square (RSME) is summarised as a goodness of fit indicator of the calibration procedure (**Table 3**).

The considered path are two urban roads thus the speed limit is constrained to the 50 km/h; the difference in terms of length is around 650 m (indeed the alternative path is 1300 m); both paths diverge from the same node and merge to the same junction (Section 4).


**Table 2.**

*Calibration results (TT) of the simulation model.*


**157**

**Table 4.**

*Centralised Traffic Control and Green Light Optimal Speed Advisory Procedure in Mixed…*

4 and 5) and the link controllers (sections 1 and 2) are represented.

• the first was only based on a traffic control procedure;

• the third was based on the combination of both sub-models.

each simulation a warm-up period taking teen minutes is considered.

• the second on speed guidance optimisation;

The tested scenarios are listed below:

The reader may refer to **Figure 3**, showing the traffic signal controllers (sections

Concerning the simulation results, it must be specified that all numerical applications were run on a server machine Intel(R) Xeon(R) CPU E5–1620 v3, clocked at 3.50GHz and with 8GB of RAM. As already anticipated in the introduction three

The simulation interval considered for each scenario is equal to one hour and for

1.the traffic control scenario [TC], the hybrid traffic control strategy combining the centralised traffic control and the link metering are applied; this strategy has been tested considered a successive bi-level mono-criterion optimisation [TCMONO] and a simultaneously multi-criteria optimisation [TCMULTI];

2.the speed guidance scenario [S-GLOSA], providing a warning to the driver concerning the optimal speed to be maintained while approaching the junction;

3.the mixed scenario [TC& S-GLOSA], both the TC strategy and the MS-GLOSA

To preliminarily compare the achieved results a further scenario has introduced as baseline. In particular, in the baseline scenario an Adaptive Signal Control [A - SC] strategy has been considered [23]. Furthermore, it must be also clarified that in all scenarios, the considered penetration rate of CAV (Connected Autonomous Vehicles) equals 50%, and the impact of the penetration rate of connected and autonomous vehicles has not yet been tested. Indeed, it will be remarked as future perspective then in terms of further issues to be investigated. In the following the results of each

In particular, in order to evaluate the effectiveness of the proposed strategy, the [A - SC] scenario was compared with each one of three scenarios [YY], and the relative difference (i.e. A - SC vs. YY) between the mean value of actual travel times of two alternative paths is then performed [TTpathx] (see **Table 4**) as well as the mean value of the relative difference of the queue lengths [QL] at significant sections (see **Table 5**; sections are identified in accordance with **Figure 3**). The results

**YY - SCENARIO Path 1 Path 2** TCMONO −18.75 −26.70 TCMULTI −25.31 −33.28 S-GLOSA −15.12 −21.27 TCMULTI&S-GLOSA −29.11 −37.22

*Mean TTS rel. Diff. [%] of [a - SC] scenario w.r.t [YY] scenario.*

*DOI: http://dx.doi.org/10.5772/intechopen.95247*

scenarios were considered in all:

are implemented.

scenario are displayed.

*(2)From Piazza Vittoria (junction 3 in Figure 3) to Via Acton.*

#### **Table 3.**

*Calibration results (QL) of the simulation model.*
