*4.1. Design Type Classification*

Table 2 shows the results of categorizing the nine study sites in the two three-category design type variables. Most, but not all, the VS and DC types were clearly defined. Geumha-ro 23-gil, Bangbaecheon-ro 2-gil, and Godeok-ro 38-gil were obviously VS-C because the stamped asphalt was paved only at the roadside, which created a clear distinction between pedestrian and vehicular zones. Sanggye-ro 5-gil and Gyeongin-ro 15-gil were ambiguous in relation to the pedestrian zone. Sanggye-ro 5-gil had a zigzag design with triangular shapes drawn in a row at the roadside. Gyeongin-ro 15-gil did not have an obvious design, but there was a strip of bright color in the middle in sharp contrast to the color used on the rest of the street. The three experts considered Sanggye-ro 5-gil as VS-B and Gyeongin-ro 15-gil as VS-A.


**Table 2.** Paving design classifications.

Yeonseo-ro 23-gil, Eunpyeong-gu

Source: © Daum Roadview (https://map.kakao.com).

Regarding the DC types, Sanggye-ro 5-gil and Dongho-ro 11-gil had transverse lines; however, only Dongho-ro 11-gil was classified as DC-B. The experts determined that the triangular features of Sanggye-ro 5-gil stood out more than the transverse lines, which weakened the lines' impacts. In addition, Sanggye-ro 3-gil and Yeonseo-ro 21-gil were identified as DC-B. Although Sanggye-ro 3-gil had an "X" mark across the street, the experts believed that drivers were unlikely to sense the segmented-street effect because the lines were too close to each other. The effects of the transverse lines at Yeonseo-ro 21-gil were also believed to be marginal because the lines were at the speed bumps.

Because the questionnaire survey covered the entire area of each site, the classification results were changed for Sanggye-ro 3-gil and Sanggye-ro 5-gil, which originally were one site; so, the VS type was merged with VS-B.

### *4.2. Before and After Comparisons of Speed by Paving Design Type*

Table 3 presents the *t*-test results, which compare the mean speeds before to those after the PPS. Regarding VS-C and DC-C, the fastest speeds were observed after the PPS. This is an unintended effect of PPS, which could occur when there is an exclusive driving zone or a lack of transverse designs. This result is still valid when we consider the mean speed of the control group, although it has not been statistically tested due to the limited data.


**Table 3.** Comparison of speed before to that after the PPS was implemented by design type..

1 The control groups were selected for each target site where the mean speed can be extracted through Seoul TOPIS (Transport Operation and Information Service) among the streets most similar and nearest to the target sites. Since it is not possible to obtain individual vehicle speed of control group, only average values are presented. (http://topis.seoul.go.kr). \* = *p* < 0.10, \*\* = *p* < 0.05, \*\*\* = *p* < 0.01.

### *4.3. Multiple Regression Results on Paving Design Types*

Tables 4 and 5 show the multiple regression results. The adjusted R<sup>2</sup> values of mean vehicle speed models were 0.71 and 0.70, which is relatively high; those of the change in speed models were 0.34 and 0.29. All of the variance inflation factors were less than 10 (data not shown). The results are explained in two table sections depending on the two classification methods (VS and DC).


**Table 4.** Multiple regression analysis by design type (dependent variable: mean vehicle speed at recording sites); *n* = 54.

> \* = *p* < 0.10, \*\* = *p* < 0.05, \*\*\* = *p* < 0.01.



\* = *p* < 0.10, \*\* = *p* < 0.05, \*\*\* = *p* < 0.01.

### 4.3.1. Results by VS Type

As expected, only VS-C was positively and significantly associated with mean speed (*p* < 0.10) after controlling for the e ffects of other factors. The finding indicates that vehicle speed was faster on average as the distinctions between the vehicular and pedestrian zones became more obvious. Moreover, VS-A and VS-B were negatively associated with the change in tra ffic speed, compared to VS-C (Table 5), meaning that VS-C had the smallest influence among the three levels of distinction in improving pedestrian safety. It also supports the contention that the application of the PPS design principles was effective.

The survey results further support this interpretation (Table 6). The percentage of respondents who answered that they experienced a decrease in vehicle speeds, collision risks, and the number of vehicles overtaking pedestrians were the lowest in the VS-C group, whereas the percentage of negative responses to these items was the highest. However, the number of positive responses on pedestrian safety was higher at VS-B sites, which ambiguously indicate pedestrian zones, than at VS-A sites, which more closely reflects the PPS principle of coexistence. There are some possible reasons for this finding. First, residents' subjective perceptions are from the pedestrian's perspective, but the change in speed reflects changes in driving behavior. In other words, even if the PPS induced deceleration, pedestrians might not perceive an improvement in safety. Moody and Melia found similar results [42,43]: Despite a significant reduction in average traffic speed and the number of traffic accidents after the shared space concept was implemented at Elwick Square in Ashford, UK, most of the pedestrians perceived that the situation was safer before the change, or they were still concerned about being hit by cars. Moreover, regardless of speed change, the respondents seemed to prefer a somewhat segregated walking space. Kaparias et al. proposed a "safe zone" in shared spaces to encourage walking freedom by increasing pedestrians' comfort [24] (p. 20). In other words, the perception of safety supposedly offered by a designated pedestrian zone might influence people's perceptions of safety.


**Table 6.** Survey result: Perceptions of pedestrian safety by Visual Separation (VS) types.

### 4.3.2. Results by DC Type

Table 4 shows that DC-C, which had no transverse designs, was statistically significant and positively related to speed change (*p* < 0.10), and Table 5 shows that DC-B was negatively associated with the differences in the mean speeds, compared to DC-C (reference group). These results sugges<sup>t</sup> that transverse markings were important in achieving the PPS goals. However, only Dongho-ro 11-gil was in the DC-A category, which may have influenced the statistical non-significance. Even so, the presence of the transverse lines seems to contribute to improving the walking environment more than their absence. A comparison of the average speed changes at the study sites after the PPS to before it was implemented, considering only the presence or absence of these lines, shows a significant speed reduction where the transverse lines were applied.

The survey data revealed a high percentage of positive opinions about safety at DC-A sites, which clearly emphasized the transverse designs (Table 7). In relation to DC-B, where the transverse designs had a smaller visual impact than DC-A, the responses were less positive about safety than they were for DC-C, which has no transverse line designs. Most of the study sites in the DC-C category were

also in the VS-C category, which presents an exclusively pedestrian zone. Thus, people's preference for clearly marked pedestrian areas might have influenced these results.

The e ffects of the control variables generally were as expected. Study sites with narrow street widths and large tra ffic and pedestrian volumes experienced slower average driving speeds after the PPS were implemented. In addition, the farther the distance to the intersection and the more speed bumps, the stronger the impact of speed change in the negative direction.


**Table 7.** Survey result: Perceptions of pedestrian safety by driving continuity (DC) type.

### **5. Conclusions and Policy Recommendations**

This study examined the influences of the PPS paving design types on safety and the perception of safety (the main goals of PPS), using video analysis and survey research. The results suggested several things. First, even when there was a di fference by type of paving design, tra ffic speeds were slower at the study sites where the PPS paving strategies were faithfully applied. Where the pedestrian and vehicular zones were clearly distinguished using PPS techniques, however, vehicle speeds were faster after than before the PPS were implemented. Vehicles traveling at high speeds are more dangerous to pedestrians when the level surfaces are used for pedestrian zones. In sum, the PPS design principles should be followed to avoid adverse outcomes.

These findings are useful for informing governmen<sup>t</sup> o fficials and residents about the value of PPS paving designs. When the PPS projects were implemented in 2014, it was di fficult to persuade residents of the value of the designs because they did not understand the projects and there were no empirical data to prove its e ffectiveness [29]. Most of the survey respondents wanted a completely independent pedestrian zone in the final design plan, which changed the original plans for several sites [29]. The municipal governments, which prioritized the local residents' opinions, ultimately used stamped asphalt pavement only for the parts of the street that would create exclusive pedestrian zones. This study's results provide evidence for avoiding that approach, which conflicts with the PPS's original intention, in future projects.

The PPS approach might be useful to other metropolitan cities with narrow asphalt streets without sidewalks. The low cost and rapid construction time are obvious advantages of using stamped asphalt pavement. Moreover, the shared space concept, which causes a paradigm shift toward coexistence among street users, might be a feasible option for solving problems with sidewalk installation. In this sense, the PPS is a reasonable transitional solution to achieve pedestrian-friendly environments, although, on the basis of our findings, its benefits might be realized only when its principles are followed.

Last, related policies are needed to ensure appropriate PPS implementation, as Kim and Shim argued, regarding promotion, speed control, guidance, and the physical improvements [58]. It is most important to legally ensure safe and convenient walking on shared streets. Currently, Korean legislation does not guarantee or protect pedestrians' rights on these streets. The Road Tra ffic Act (Article 8) states that, "on a road that is not divided into a sidewalk and a roadway, pedestrians shall walk on the fringe of the road in the direction opposite to horses and vehicles or the side of the road" [61]. Until the law protects pedestrians' right to unrestricted walking on *organically* shared streets, people are compelled to walk defensively, even on the PPS streets.

Despite its contributions, this study has several limitations. Although we obtained speed data on every vehicle that passed through the recording spots of the study sites, we had to average them, and other information about individual vehicles, such as driver characteristics, travel purposes, and so on was not available. This limitation might have created an ecological fallacy. Because the number of values decreased by using the mean, it was di fficult to simultaneously verify all the types of PPS designs. To overcome these limitations, we analyzed separate regression models. We also could not fully control for the e ffects of natural changes over time because the design and data did not allow for testing a control group; however, we minimized the e ffects of these limitations by using the nine PPS sites that were concurrently completed.

More discussion is needed regarding the establishment of distinct pedestrian zones at PPS sites. We tried to inform this discussion by classifying the design types in two ways, but conflicting results were found depending on the perspective. Although safety was objectively determined as better when the PPS principles were followed, there was a gap between the objective results and the residents' subjective perceptions about safety. It would be helpful to harmonize these points through future research, in order to help improve future PPS plans.

**Author Contributions:** S.-N.K. developed the research topic and framework, carried out the data collection and initial analysis, and drafted some parts of the manuscript. H.L. drafted most of the manuscript and was involved in the literature review, data analysis, and interpretation of research findings. All authors read and approved the manuscript.

**Funding:** This research was supported by the Chung-Ang University Graduate Research Scholarship in 2018. This work was also partially supported by the National Research Foundation of Korea (NRF) gran<sup>t</sup> funded by the Korea governmen<sup>t</sup> (MSIT) (No. NRF-2018R1C1B6008235).

**Acknowledgments:** The authors are grateful to the anonymous reviewers for their excellent suggestions for improving the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
