# Analysis of Perception Accuracy of Roadside Millimeter-Wave Radar for Traffic Risk Assessment and Early Warning Systems

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## Abstract

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## 1. Introduction

## 2. Related work

#### 2.1. Traffic Risk Assessment and Early Warning Systems

#### 2.2. Radar Perception Accuracy Analysis

## 3. Factors Influencing Positioning Accuracy

#### 3.1. Radar Detection Principles

#### 3.1.1. Signal Processing Module

#### 3.1.2. Data Processing Module

#### 3.2. Analysis of the Factors Influencing Positioning Accuracy

#### 3.2.1. Radar Installation Height

#### 3.2.2. Radar Sampling Frequency

#### 3.2.3. Vehicle Location

#### 3.2.4. Vehicle Posture

#### 3.2.5. Vehicle Size

## 4. Simulation Results

#### 4.1. Influence of Radar Installation Height

#### 4.2. Influence of Radar Sampling Frequency

#### 4.3. Influence of Vehicle Location

#### 4.4. Influence of Vehicle Posture

#### 4.5. Influence of Vehicle Size

## 5. Guidelines for MMW Radar Data Processing

#### 5.1. Data Filtering Based on Vehicle Location

#### 5.2. Data Filtering Based on Vehicle Posture

#### 5.3. Measurement Adjustment Based on Vehicle Size

## 6. Conclusions

- Influence of radar installation height: When the radar is installed at a higher position with a greater pitch angle to monitor the same section of road, a larger longitudinal positioning error is observed when the vehicle is driving away from the radar FOV.
- Influence of radar sampling frequency: Greater tracking error on the y-direction is observed when the sampling frequency is lower. The tracking error on the x-direction is not significantly influenced by the sampling frequency.
- Influence of vehicle location: When the vehicle passes through the radar FOV, the radar positioning in the longitudinal direction is first positively and then negatively biased. In the lateral positioning, the radar positioning biases to the left when the vehicle locates on the right side of the radar central beam, and vice versa.
- Influence of vehicle posture: A large positioning deviation is observed when the vehicle yaw angle is at $\pm 90\xb0$.
- Influence of vehicle size: When the vehicle is closer to the radar module, the vehicle height can severely affect longitudinal positioning. The vehicle length causes longitudinal positioning errors when the vehicle is further from the radar module. A greater lateral positioning error is observed when the vehicle is wider.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 3.**FMCW ranging: $f$ shows the frequencies of the transmitted and received signals, ${f}_{\Sigma}$ the frequency of the beat signal, $\Delta f$ the maximum frequency offset, ${f}_{{b}^{+}}$ and ${f}_{{b}^{-}}$ the positive and negative beat frequencies, respectively ${f}_{\mathit{bav}}$ the average beat frequency, and ${f}_{m}$ and ${T}_{m}$ the frequency and period of the triangular wave, respectively.

**Figure 4.**MMW radar angle measurement: TX and RX are the transmitting and receiving antennas, respectively, $d$ the distance between two antennas, and $\theta $ the target angle.

**Figure 8.**Variation in the tracking results regarding radar sampling frequency: (

**a**) high sampling frequency; (

**b**) low sampling frequency.

**Figure 11.**Radar installation schemes: (

**a**) front top mounting; (

**b**) side top mounting; (

**c**) side mounting.

**Figure 12.**Variation in point cloud distribution regarding vehicle posture: (

**a**) yaw angle $0\xb0$; (

**b**) yaw angle $45\xb0$; (

**c**) yaw angle $90\xb0$.

**Figure 17.**Radar positioning error based on radar installation height; $x$ and $y$ denote the vehicle positions in the world coordinate system, and $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions, respectively: (

**a**) $\mathsf{\Delta}x-x$; (

**b**) $y-\mathsf{\Delta}y$.

**Figure 18.**Radar positioning error based on MMW radar sampling frequency; $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions in world coordinates, respectively: (

**a**) $\mathsf{\Delta}x$ based on sampling frequency; (

**b**) $\mathsf{\Delta}y$ based on sampling frequency.

**Figure 20.**Radar positioning error based on vehicle location; $x$ and $y$ denote the vehicle positions in the world coordinate system, and $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions, respectively: (

**a**) $\mathsf{\Delta}x-x$; (

**b**) $x-\mathsf{\Delta}y$; (

**c**) $\mathsf{\Delta}x-y$; (

**d**) $y-\mathsf{\Delta}y$.

**Figure 21.**Radar positioning error based on vehicle yaw angle; $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions in world coordinates, respectively, and $\phi $ denotes the vehicle yaw angle.

**Figure 22.**Radar positioning error based on vehicle length; $x$ and $y$ denote the vehicle positions in the world coordinate system, $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions, respectively, and $\phi $ denotes the vehicle yaw angle.

**Figure 23.**Radar positioning error based on vehicle width; $x$ and $y$ denote the vehicle positions in the world coordinate system, $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions, respectively, and $\phi $ denotes the vehicle yaw angle.

**Figure 24.**Radar positioning error based on vehicle height; $x$ and $y$ denote the vehicle positions in the world coordinate system, $\mathsf{\Delta}x$ and $\mathsf{\Delta}y$ denote radar positioning errors in the x- and y-directions, respectively, and $\phi $ denotes the vehicle yaw angle.

**Table 1.**Effective scatterers and the number of measured points in different longitudinal locations.

Vehicle Longitudinal Location | Effective Scatterer | Measured Points |
---|---|---|

Partial entry | Front | Few |

Full entry | Body and rear | Many |

Driving away | Rear | Some |

Parameters | Value | Unit |
---|---|---|

Center frequency | 77 × 10^{9} | Hz |

Range limits | 150 | m |

Azimuthal field of view | 20 | degree |

Elevation field of view | 5 | degree |

Range rate limits | 100 | m/s |

Azimuth resolution | 4 | degree |

Range resolution | 2.5 | m |

Range rate resolution | 0.5 | m/s |

Update rate | 100 | Hz |

Installation position | (0, 0, 5) | m |

Installation pose | (0, 5, 0) | degree |

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## Share and Cite

**MDPI and ACS Style**

Zhao, C.; Ding, D.; Du, Z.; Shi, Y.; Su, G.; Yu, S.
Analysis of Perception Accuracy of Roadside Millimeter-Wave Radar for Traffic Risk Assessment and Early Warning Systems. *Int. J. Environ. Res. Public Health* **2023**, *20*, 879.
https://doi.org/10.3390/ijerph20010879

**AMA Style**

Zhao C, Ding D, Du Z, Shi Y, Su G, Yu S.
Analysis of Perception Accuracy of Roadside Millimeter-Wave Radar for Traffic Risk Assessment and Early Warning Systems. *International Journal of Environmental Research and Public Health*. 2023; 20(1):879.
https://doi.org/10.3390/ijerph20010879

**Chicago/Turabian Style**

Zhao, Cong, Delong Ding, Zhouyang Du, Yupeng Shi, Guimin Su, and Shanchuan Yu.
2023. "Analysis of Perception Accuracy of Roadside Millimeter-Wave Radar for Traffic Risk Assessment and Early Warning Systems" *International Journal of Environmental Research and Public Health* 20, no. 1: 879.
https://doi.org/10.3390/ijerph20010879