# Crosswalk Safety Warning System for Pedestrians to Cross the Street Intelligently

^{*}

## Abstract

**:**

## 1. Introduction

## 2. System Design

#### 2.1. Detection Module

#### 2.1.1. Vehicle Inspection

_{a}(m/s) [23] is as follows:

_{0}(m/s) at which the vehicle can safely stop from the virtual coil to the parking line. The v

_{0}is derived from the inverse of the parking sight distance model [24], as follows:

^{2}), generally taken as 9.8 m/s

^{2}; $\phi $ is the humidity coefficient, taken as 0.4 in the more humid situation; $\varphi $ is the roughness coefficient, taken as 0.03~0.05.

_{0}that the vehicle can safely stop from is inferred from Equation (3), the vehicle is judged to be at a safe speed by comparing the initial running speed v

_{0}with the average speed v

_{a}of the vehicle driving through the virtual coil.

#### 2.1.2. Pedestrian Detection

_{b}is the movement speed of the target relative to the radar (m/s); v

_{p}is the pedestrian step speed (m/s).

#### 2.2. Control Module

_{p}is the pedestrian crossing travel time (s); L

_{c}is the single-lane width; k is the number of lanes (m); ${x}^{\prime}$ and ${y}^{\prime}$ are the number of pedestrians on the left and right sides of the crosswalk; s is the safety factor, generally taken as 5.

_{p}and the remaining passage time u of the pedestrian signal, the system can determine whether the pedestrian can finish crossing the street or reach the safety island in the middle of the road.

- (1)
- Case 1. If there is a vehicle stopped, the red light of the zebra crossing in front of the lane where the pedestrian is located and the next lane ahead is controlled to flash (see Figure 5a), thus, preventing the vehicle driver from starting due to inattention [28] or negligent observation when the signal is switched, and causing a traffic accident;
- (2)
- Case 2. If no vehicle is currently stopped and there is a vehicle approaching above a safe speed, the red warning of the crosswalk in front of the next lane ahead is controlled (see Figure 5b), thus, warning vehicles and pedestrians of the impending danger;
- (3)
- Case 3. If no vehicle is currently stopped and a vehicle not exceeding the safe speed is approaching, the yellow warning of the zebra crossing in front of the next lane ahead is controlled (see Figure 5c), thus, warning drivers and pedestrians to pass when it is judged safe to do so.

#### 2.3. Warning Module

#### 2.4. Wireless Communication Module

## 3. Vehicle Safety Braking Distance Model Considering Human–Vehicle Characteristics

#### 3.1. Vehicle Minimum Safe Braking Distance Model Improvement

#### 3.2. Vehicle Minimum Safe Braking Distance Model Improvement

_{p}is the safe psychological distance for pedestrians to cross the street (m); v

_{i}is the speed of the ith lane (m/s); n is the number of lanes; L

_{c}is the width of a single lane (m); t

_{r}is the pedestrian reaction time (s), with an average value of 1.8 s; C

_{s}is the safe distance of the arriving vehicle from the pedestrian (m), taken as 3–5 m.

_{j}is the vehicle braking deceleration (m/s

^{2}); $\delta $ is the rotating mass conversion factor, generally taken as 1.1 to 1.4.

_{s}in Equation (11) can be neglected due to the large number of factors considered and the increase in the influence parameter of the model. In summary, by substituting and combining Equations (11)–(13), the pedestrian psychological safety braking distance ${L}_{\mathrm{p}}^{\prime}$ can be obtained as follows:

#### 3.3. Modelling of Safe Braking Distances considering Human and Vehicle Characteristics

_{0}value for each lane gives a safe braking distance model that takes into account the characteristics of people and vehicles, as follows:

_{0}and weight $\beta $ on the model, the other factors are taken as constant values, resulting in a vehicle safety braking distance surface that takes into account the human–vehicle characteristics, as shown in Figure 11.

## 4. Comparative Model Analysis

_{0}and the weight $\beta $ are calibrated and taken uniformly.

^{2}; the dampness factor $\phi $ is taken as 0.4 for wetter conditions; the roughness factor $\varphi $ is taken as 0.04; the longitudinal slope of the road $\theta $ is taken as 0; the safety distance ${l}_{0}$ is taken as 5 m; only the case of pedestrians crossing a lane is discussed, and the number of lanes n is taken as 1; the width of a single lane L

_{c}is set as 3.5 m. The pedestrian crossing speed v

_{p}is taken as the general standard speed of 1.5 m/s; the pedestrian reaction time t

_{r}is taken as the average value of 1.8 s; the distance C

_{s}between the arriving vehicle and the pedestrian is taken as 3 m; the rotating mass conversion factor $\delta $ is taken as 1.2; the vehicle braking deceleration a

_{j}is obtained as 3.6 m/s

^{2}; the pedestrian characteristic parameter K is taken as 1 according to the general situation; the target body length ${a}_{0}$ and height ${b}_{0}$ are determined according to the dimensions of ordinary small cars are 4.8 m and 1.4 m, respectively; the body length ${a}^{*}$ and height ${b}^{*}$ of the reference vehicle are taken as 5 m and 1.6 m, respectively.

_{0}of the vehicles. At the same time, the weight $\beta $ in the vehicle safety braking distance model considering the human–vehicle characteristics was taken from 0.5 to 1 in intervals of 0.1 to calculate the safety distance solved by the model at different weights, and the safety distance comparison curve is shown in Figure 12. As can be seen from the figure, the pedestrian psychological safe braking distance is much greater than the braking distance of the vehicle at the same speed so, in practice, if only the traditional stopping sight distance model is used, it does not meet the pedestrian psychological requirements for distance. The vehicle safety braking distance model considering human–vehicle characteristics, takes into account the pedestrian psychology and gives different weights to the vehicle and the pedestrian, while taking into account the fact that a long safety braking distance is difficult to achieve in practice, so that the safety braking distance is increased to a certain extent without increasing too much, giving the pedestrian a certain psychological mitigation distance. To a certain extent, the psychological impact on pedestrians caused by excessive speed or stopping too close to them is avoided, and the safe braking distance is reasonable. It can also be seen that the ${S}_{0}^{\prime}$ curve is slightly higher than the ${S}_{0}$ curve, indicating that the improved vehicle safety braking distance is greater than the stopping sight distance, meaning that safety is improved; the increase in braking distance is more limited and can more realistically reflect the distance travelled by the vehicle during the brief braking force rise that is ignored in the stopping sight distance model.

## 5. Conclusions

- (1)
- The designed system detects the position and speed of pedestrians and vehicles in real-time, discriminates between pedestrian and vehicle conflicts with reference to the situation, and runs different warning schemes for different situations. Warning for pedestrians through voice prompting stakes, and two-way warning for pedestrians and vehicles through intelligent zebra crossings with the onset of red, red flashing, yellow lights can effectively reduce conflicts between pedestrians and vehicles and avoid traffic accidents;
- (2)
- The proposed model incorporates considerations of pedestrian psychological safety distances and the impact on vehicle models based on an improved vehicle stopping sight distance model, resulting in further improvements in vehicle braking safety while reducing the psychological impact of the braking process on pedestrians.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Composition of crosswalk safety warning system for pedestrians to cross the street intelligently.

**Figure 3.**Image differential signal output generated when the vehicle passes through the virtual coil Loop1 and Loop2.

**Figure 5.**Intelligent crosswalk warning schematic. (

**a**) Case 1 Red light flashing; (

**b**) Case 2 Red light warning; (

**c**) Case 3 Yellow light warning.

**Figure 6.**Control flow of control module in crosswalk safety warning system for pedestrians to cross the street intelligently. Here, u is time remaining for the pedestrian green light (s), and t

_{p}is time required for pedestrian crossing (s).

**Figure 9.**Wireless communication module in crosswalk safety warning system for pedestrians to cross the street intelligently.

**Figure 10.**Simplified vehicle braking process schematic, where ${t}_{0}={t}_{0}^{\prime}+{t}_{0}^{\u2033}$ is the driver braking reaction time (s), ${t}_{1}$ is the braking deceleration generation time (s), ${t}_{2}$ is the braking deceleration rise time (s), ${t}_{3}$ is the braking duration (s), and ${t}_{4}$ is the braking deceleration removal time (s).

**Figure 11.**3D surface diagram of vehicle safety braking distance model considering human–vehicle characteristics.

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## Share and Cite

**MDPI and ACS Style**

Qu, D.; Li, H.; Liu, H.; Wang, S.; Zhang, K.
Crosswalk Safety Warning System for Pedestrians to Cross the Street Intelligently. *Sustainability* **2022**, *14*, 10223.
https://doi.org/10.3390/su141610223

**AMA Style**

Qu D, Li H, Liu H, Wang S, Zhang K.
Crosswalk Safety Warning System for Pedestrians to Cross the Street Intelligently. *Sustainability*. 2022; 14(16):10223.
https://doi.org/10.3390/su141610223

**Chicago/Turabian Style**

Qu, Dayi, Haiyang Li, Haomin Liu, Shaojie Wang, and Kekun Zhang.
2022. "Crosswalk Safety Warning System for Pedestrians to Cross the Street Intelligently" *Sustainability* 14, no. 16: 10223.
https://doi.org/10.3390/su141610223