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\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Speed of Collision (km/h)** & 80 & 65 & 50 & 32 \\ \hline
**Chance of Pedestrian Death (\%)** & 100 & 80 & 40 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chance of pedestrian death if hit by a motor vehicle. speed humps and bumps, is limited to short distances [49] and is believed to cause disturbance in traffic flow and smoothness. When applied inappropriately, i.e., the distance between devices are too short or too long, they can push drivers to an aggressive style instead of keeping them within assumed limits. Frequent deceleration and acceleration maneuvers may also lead to additional dangerous behavior due to lack of speed uniformity [31; 50]. Although a number of studies have been dedicated to the assessment of the various effects of individual traffic calming measures [21; 30; 51], there is still a lack of information on the relative impact and effectiveness of vertical shifts implemented in sequence. The first traffic calming measures in the US were often spaced at intervals over 150 m (500 feet) and it was found that at the midpoint no speed reduction was achieved. However, if they were very near, they even became a problem. In Bellevue (US) speed humps spaced 45.75 m (150 feet) were removed to provide a distance of 91.5 m (300 feet) [29]. [PERSON] [52] showed how speed in the middle points could be related to the distance between TCMs (Figure 1) from data from different countries. Research in the US indicated a speed increase of approximately 0.8 to 1.6 km/h (0.5 to 1.0 mile/h) for every 30.5 m (100 feet) of spacing between humps for distances below 305 m [29]. Nevertheless, commented researches were conducted in the 20 th century in residential areas in the suburbs of the big cities in the USA. Since then, there has been a great spreading on the employment of TCM around the world. At present, in Europe TCMs are mainly placed in city centers, in downtowns, trying to make these areas more peaceful with the aim of providing friendly spaces for pedestrians, from both the point of view of road safety and the environment [21; 35; 38; 53; 54; 55]. Moreover, nowadays, drivers are more used to this kind of speed control measures. Nonetheless, scarce literature can be found about the adequate distance between them. [PERSON] et al. [54] studied the influence of the distance between TCMs on the capacity of cross-town road and conclude that a range between 50 and 400 m was critical. [PERSON] and [PERSON] [55] observed that variable spacing influenced the median speed in the intermediate points of the segments, but without providing any specific relationship. [PERSON] et al. [56] analyzed the influence of speed humps on the 85 th percentile of the speed distribution and suggested that a spacing of 20 m to achieve a speed of 30 km/h, and a maximum of 70 m. Similarly, [PERSON] et al. [57] concluded that when two TCMs were spaced more than 200 m, drivers accelerate until 10 km/h over the speed limit of 50 km/h and recommended a spacing of 150-200 m, 100 m and 75 m for speed limits of 50, 40 and 30 km/h, respectively. Therefore, the aim of this paper is to analyze the speed in the intermediate points between vertical traffic calming measures and relate it with the distance between them to propose models for predicting the speed in those midpoints. For this purpose, measures were taken in stretches with successive vertical deflections in Poland and in Spain to observe drivers' behavior in different countries. Figure 1: Speed at intermediate points (km/h) as a function of the distance (m) between slow points with data from various countries. The manuscript is organized as follows: Section 2 presents the selected streets where speed data were collected. In Section 3, results are presented and discussed. Finally, Section 4 summarizes the obtained conclusions.