*3.4. Fuel Consumption Analysis*

For fuel consumption analysis, a simplified model of intersection No. 3 in the Synchro 7 program was prepared [94] (Figure 11).

With the use of this model, calculations of the efficiency indicators related to fuel consumption were made:


Results of the analysis are presented in Section 4.5 (Discussion section).

**Figure 11.** Model of intersection No. 3 in Synchro 7 and SimTraffic.

### *3.5. Case Study of a Road Crash on an Intersection with SCT*

Some of the SCTs installed at intersections in Poland work independently of other devices of this type and are not connected to the signal controller. The SCT analyzes the displayed signals from the signal cable, calculates the signals' duration, and then displays the values in the next cycle on this basis. This device is only intended for fixed-time control. The principle of operation of such a device results in displaying erroneous indications in the event of a change in the duration of signals. Such changes take place, for example, when the signaling program is changed. A case study of a road crash with such a mechanism in Szczecin (Poland) is presented below. The event took place in 2016 at the intersection of Niepodległo´sci Avenue and Zołnierza Polskiego Square. SCTs with an RSCT function and ˙ a GSCT were installed on both intersection approaches, located on mast arms to the right of the signals.

Before the event, approach A SCT had counted green, and approach B SCT had counted red (Figure 12a). After reaching the duration of the green signal, as in the previous cycle, the GSCT at approach A was off, while the green signal continued, most likely due to a change in the signaling program. At approach B, there was a countdown for the RSCT. There was little traffic at approach A (Figure 12b).

After counting down the RSCT time at approach B, the vehicles started to move even though the signal heads were showing a red signal (Figure 12c). This could be caused by too early a start, when the RSCT was displaying, for example, 1 s to display a green signal, or the situation described in [66], indicating that more drivers, before starting, were watching the RSCT than the actual signal head. As a consequence of such driver behavior and the way the SCT functioned at the intersection, a road accident occurred between the vehicle marked with a red arrow and the vehicle marked with a green arrow (Figure 12d).

**Figure 12.** Sequence of events related to the crash: (**a**) GSCT and RSCT at intersection approaches; (**b**) extinction of GSCT at approach A; (**c**) extinction of RSCT at approach B, early start of vehicles at approach B; (**d**) road accident. (Background map Main Office of Geodesy and Cartography).

#### **4. Discussion**

#### *4.1. Influence of SCT on Driver's Behavior*

If the SCT is installed and working at the intersection, the driver has more information about the working of traffic lights. The hypothesis is that SCTs influence the behavior of drivers. Devices have been installed in Płock since 2011 (six years before conducting the study). This means that the drivers moving around the city already had learned the daily rules by which these devices operate. The SCT in Płock turned off 5 s before the beginning of the red signal. The day-to-day tests increased the value of the obtained data under similar road conditions.
