Method for assisting visually impaired people to pass through pedestrian crosswalk line

Abstract

The invention relates to the technical field of traffic signal control, in particular to a method for assisting a visually impaired person to pass through a pedestrian crossing line. The data processing terminal is used for receiving real-time motion data collected by the 360-degree thermal imaging holder and the laser radar. Under the action of a control signal sent by the data processing terminal, the road warning screen can remind a driver to pay attention to the visually impaired person by means of real-time display of text content, and the voice broadcast device can remind the driver to pay attention to the visually impaired person by means of real-time voice broadcast content. And the visually impaired people can know that the visually impaired people are located in the pedestrian crosswalk line area. Therefore, on one hand, the technical transformation from'civil defense 'to'technical defense' is realized, the problem that visually impaired people safely pass through the pedestrian crosswalk line is solved, the method can be widely applied to pedestrian crosswalk line scenes with poor street crossing sight distance, and visual defects of people are made up by utilizing'technical defense '; on the other hand, visually impaired people can be intelligently screened out and tracked in real time.

Description

Technical Field

[0001] The invention relates to the technical field of traffic signal control, in particular to a method for assisting visually impaired people to cross a pedestrian crossing. Background Art

[0002] According to statistics, China has the largest group of visually impaired people in the world, with the number reaching 17.31 million in 2022. The number of new visually impaired people is 450,000 per year. At present, China's barrier-free settings lag far behind those of countries such as Singapore and Japan, and the visually impaired in China are still unable to go out.

[0003] At present, pedestrian crossing reminder facilities are mainly for normal pedestrian crossing, mainly to remind motor vehicles on the road that there are pedestrians on the crosswalk ahead. Pedestrians need to choose the right time to cross according to the traffic conditions on the road. However, when crossing the crosswalk, visually impaired people cannot effectively perceive the traffic conditions on the road, cannot observe the specific conditions of the road and the surrounding area, and find it difficult to choose the right time to cross the crosswalk and cannot perceive the safety of crossing the street ahead, resulting in the inability of visually impaired individuals to effectively cross the crosswalk. More importantly, the green light duration of the crosswalk is fixed, and it cannot be adjusted intelligently according to the specific traffic conditions of the crosswalk. Visually impaired people do not have the ability to cross the crosswalk within the limited time, and the safe crossing needs of the visually impaired cannot be guaranteed. Therefore, technical personnel are urgently needed to solve the above problems. Summary of the invention

[0004] Therefore, in view of the above-mentioned existing problems and defects, the designers of the present invention collected relevant information, conducted multiple evaluations and considerations, and continued to experiment and modify after many years of R&D experience in this industry, which ultimately led to the emergence of a method for assisting visually impaired people to cross the crosswalk.

[0005] In order to solve the above technical problems, the present invention relates to a method for assisting visually impaired persons to cross a crosswalk, which is achieved by means of facilities for assisting visually impaired persons to cross a crosswalk. Facilities for assisting visually impaired persons to cross a crosswalk include a monitoring pole, a 360° thermal imaging pan-tilt head, a laser radar, a data processing terminal, a road warning screen, and a voice broadcast device. The monitoring pole is erected on one side of the crosswalk, and its cantilever beam spans the crosswalk. The 360° thermal imaging pan-tilt head is installed on the cantilever beam of the monitoring pole, and it is aligned with the center position of the crosswalk. Multiple laser radars use the cantilever beam of the monitoring pole as the installation base, and are linearly evenly distributed along its length. The road warning screen and the voice broadcast device are both installed on the upright pole body of the monitoring pole. The data processing terminal is used to receive real-time motion data collected by the 360° thermal imaging pan-tilt head and the laser radar. Under the control signal from the data processing terminal, the road warning screen can use real-time text display to remind the driver that the visually impaired are slowly crossing the crosswalk area, and the voice broadcast device can use real-time voice broadcast content to remind the driver that the visually impaired are slowly crossing the crosswalk area, and the visually impaired knows that they are in the crosswalk area by receiving the voice broadcast content.

[0006] The method for assisting the visually impaired to cross the pedestrian crossing line includes the following steps:

[0007] S1. Use a 360° thermal imaging gimbal to take thermal images of pedestrians crossing the crosswalk, and screen out visually impaired people based on the speed curve, and transmit the collected thermal images of visually impaired people to the data processing terminal in real time. Use a laser radar to scan the moving vehicles, and transmit the collected radar point cloud images to the data processing terminal in real time;

[0008] S2. Calibrate the parameters of the thermal image and the radar point cloud image, and adjust the clock sources of the two to be unified and the timestamps to be consistent;

[0009] S3. The data processing terminal determines the real-time specific position and moving speed V of the visually impaired person based on the thermal image. 人 , and estimate the time T required for a visually impaired person to cross the crosswalk 人 , and the data processing terminal determines the real-time specific position and moving speed V of the vehicle based on the radar point cloud image 车 , and estimate the time T required for the vehicle to reach the crosswalk 车 ;

[0010] S4, if T 车 >>T 人 , the vehicle passes normally; if not, the data processing terminal sends a control signal to the road warning screen and voice broadcasting equipment.

[0011] As a further improvement of the technical solution disclosed in the present invention, in step S4, at T 车 Not much larger than T 人 In the case of L 车 <T 车 *V 人 , the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "Pedestrians Stop and Wait" in a scrolling manner, and the voice broadcast device repeatedly plays the "Pedestrians Stop and Wait" prompt sound; after the vehicle passes the crosswalk, the data processing terminal again sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "Pedestrians Pass" in a scrolling manner, and the voice broadcast device repeatedly plays the "Pedestrians Pass" prompt sound; if L 车 ≥T 车 *V 人 , the vehicle stops passing, and the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device. The road warning screen displays the text content "Vehicle Stop Waiting" in a scrolling manner, and the voice broadcast device repeatedly plays the "Vehicle Stop Waiting" prompt sound.

[0012] As a further improvement of the technical solution disclosed in the present invention, the color change process of the signal traffic light is controlled by the data processing terminal; 车 ≥T 车 *V 人 In this case, the signal traffic light remains at red until the visually impaired person completely crosses the crosswalk.

[0013] As a further improvement of the technical solution disclosed in the present invention, in step S1, the thermal image is composed of a plurality of thermal image frames played in time sequence. The collected thermal image frames are subjected to binary threshold processing by means of a data processing terminal. During the binary threshold processing, when the distance between two adjacent pixels in the thermal image frame is less than a set threshold A1, they are merged into a cluster, and the cluster is set with a maximum lower limit.

[0014] As a further improvement of the technical solution disclosed in the present invention, in step S1, the generation process of the thermal image includes the following stages: the image collected by the 360° thermal imaging gimbal is processed by morphological filtering and threshold segmentation in sequence to obtain a binary image. The center of the 360° thermal imaging gimbal is used as the coordinate origin to establish an image coordinate system, and the binary image is placed in the image coordinate system, and the binary image is traversed to determine the specific position of the visually impaired person.

[0015] As a further improvement of the technical solution disclosed in the present invention, in step S2, the thermal image is taken in a two-dimensional coordinate system [u 人 , v 人]T for calibration, and the radar point cloud image adopts a two-dimensional coordinate system [u 车 , v 车 ]T is calibrated; assuming that the resolution of the thermal image is A, then A=L×Q, where L is the number of pixels in the height direction and Q is the number of pixels in the horizontal direction.

[0016] As a further improvement of the technical solution disclosed in the present invention, the facilities for assisting the visually impaired to cross the pedestrian crossing also include an intelligent sensing electronic device. The intelligent sensing electronic device interacts with the data processing terminal and is carried or worn by the visually impaired.

[0017] As a further improvement of the technical solution disclosed in the present invention, the facility for assisting the visually impaired to cross the pedestrian crossing line also includes an embedded solar road stud. A plurality of embedded solar road studs are arranged in a linear array on one side of the pedestrian crossing line, and do not protrude from the road surface after being embedded.

[0018] In the technology disclosed in the present invention, the facilities for assisting the visually impaired to cross the crosswalk integrate the "sound and light" technology to meet the needs of the visually impaired to cross the crosswalk safely. During this period, the 360° thermal imaging pan / tilt and laser radar are used to continuously monitor the position information of road vehicles and pedestrians who want to cross the street, and the monitored data is transmitted to the data processing terminal, and the visually impaired are screened and determined according to the speed curve. And according to the relative coordinate positions of the vehicles and the visually impaired monitored at different times, the speed of the vehicle and the time required to reach the crosswalk are calculated, and the speed of the visually impaired and the time required to completely cross the crosswalk are calculated. Based on this, the data processing terminal intelligently gives corresponding processing measures, and communicates with the road warning screen and voice broadcasting equipment, so that the traffic information of the crosswalk is transmitted to the vehicle and the visually impaired in the first time.

[0019] In practical applications, the method for assisting visually impaired persons to cross a pedestrian crossing disclosed in the present invention can achieve at least the following beneficial technical effects, specifically:

[0020] 1) When a visually impaired person is crossing a pedestrian crossing, a voice announcement device is used to make the visually impaired person aware that he or she is in the pedestrian crossing area and to inform him or her of the corresponding measures to ensure the personal safety of the visually impaired person when crossing the pedestrian crossing;

[0021] 2) The facilities for assisting the visually impaired to cross the crosswalk can intelligently screen out the visually impaired and track them in real time. When a visually impaired person crosses the crosswalk, the oncoming vehicle will be informed in advance so that the driver can slow down or stop the vehicle in advance. Furthermore, it can also solve the problem that the driver cannot immediately find the pedestrian crossing the crosswalk due to poor lighting at night, poor road visibility, or bad weather;

[0022] 3) It has realized the technological transformation from "human defense" to "technical defense", which not only meets the problem of visually impaired people crossing the crosswalk safely, but can also be widely used in crosswalk scenes with poor sight distance when crossing the street. "Technical defense" is used to make up for human visual defects, and the safety of crosswalks can be guaranteed even in conditions of poor sight distance such as bad weather. DETAILED DESCRIPTION

[0023] In order to facilitate those skilled in the art to fully understand the technical solutions disclosed in the present invention, the contents of the present invention are further described in detail below in conjunction with specific embodiments.

[0024] The present invention relates to a method for assisting visually impaired persons to cross a pedestrian crossing, which is achieved by means of facilities for assisting visually impaired persons to cross a pedestrian crossing. Facilities for assisting visually impaired persons to cross a pedestrian crossing include a monitoring pole, a 360° thermal imaging pan-tilt head, a laser radar, a data processing terminal, a road warning screen, and a voice broadcasting device. The monitoring pole is erected on one side of the pedestrian crossing, and its cantilever beam crosses the pedestrian crossing. The 360° thermal imaging pan-tilt head is installed on the cantilever beam of the monitoring pole, and it is aligned with the center position of the pedestrian crossing. Multiple laser radars use the cantilever beam of the monitoring pole as an installation base, and are linearly evenly distributed along its length. The road warning screen and the voice broadcasting device are both installed on the vertical pole body of the monitoring pole. The data processing terminal uses the vertical pole body of the monitoring pole as an installation base, and is used to receive real-time motion data collected by the 360° thermal imaging pan-tilt head and the laser radar. Under the control signal from the data processing terminal, the road warning screen can use real-time text display to remind the driver that the visually impaired are slowly crossing the crosswalk area, and the voice broadcast device can use real-time voice broadcast content to remind the driver that the visually impaired are slowly crossing the crosswalk area, and the visually impaired knows that they are in the crosswalk area by receiving the voice broadcast content.

[0025] The facilities for assisting the visually impaired to cross the crosswalk integrate "sound and light" technology to meet the needs of the visually impaired to cross the crosswalk safely. During this period, the 360° thermal imaging pan / tilt and laser radar are used to continuously monitor the location information of road vehicles and pedestrians who want to cross the street. At the same time, the monitored data is transmitted to the data processing terminal, and the visually impaired are screened and identified based on the speed curve. And according to the relative coordinate positions of the vehicles and visually impaired people monitored at different times, the speed of the vehicle and the time required to reach the crosswalk are calculated, and the speed of the visually impaired and the time required to completely cross the crosswalk are calculated. Based on this, the data processing terminal intelligently gives corresponding processing measures and communicates with the road warning screen and voice broadcasting equipment to ensure that the traffic information of the crosswalk is transmitted to the vehicle and the visually impaired as soon as possible.

[0026] The present invention also discloses a method for assisting visually impaired people to cross a pedestrian crossing, which comprises the following steps:

[0027] S1. Use a 360° thermal imaging gimbal to take thermal images of pedestrians crossing the crosswalk, and screen out visually impaired people based on the speed curve, and transmit the collected thermal images of visually impaired people to the data processing terminal in real time. Use a laser radar to scan the moving vehicles, and transmit the collected radar point cloud images to the data processing terminal in real time;

[0028] The thermal image is composed of multiple thermal image frames played in time sequence. The collected thermal image frames are subjected to binary threshold processing by means of a data processing terminal. During the binary threshold processing, when the distance between two adjacent pixels in the thermal image frame is less than the set threshold A1, they are merged into a cluster, and the cluster is set with a maximum lower limit value;

[0029] S2. Calibrate the parameters of the thermal image and the radar point cloud image, and adjust the clock sources of the two to be unified and the timestamps to be consistent;

[0030] S3. The data processing terminal determines the real-time specific position and moving speed V of the visually impaired person based on the thermal image. 人 , and estimate the time T required for a visually impaired person to cross the crosswalk 人 , and the data processing terminal determines the real-time specific position and moving speed V of the vehicle based on the radar point cloud image 车 , and estimate the time T required for the vehicle to reach the crosswalk 车 ;

[0031] S4, if T 车 >>T 人 , the vehicle passes normally; if not, the data processing terminal sends a control signal to the road warning screen and voice broadcasting equipment.

[0032] In T 车 Not much larger than T 人 In the case of L 车 <T 车 *V 人 , the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "Pedestrians Stop and Wait" in a scrolling manner, and the voice broadcast device repeatedly plays the "Pedestrians Stop and Wait" prompt sound; after the vehicle passes the crosswalk, the data processing terminal again sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "Pedestrians Pass" in a scrolling manner, and the voice broadcast device repeatedly plays the "Pedestrians Pass" prompt sound; if L 车 ≥T 车 *V 人, the vehicle stops passing, and the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device. The road warning screen displays the text content "Vehicle Stop Waiting" in a scrolling manner, and the voice broadcast device repeatedly plays the "Vehicle Stop Waiting" prompt sound.

[0033] In practical applications, the method for assisting visually impaired persons to cross a pedestrian crossing disclosed in the present invention can achieve at least the following beneficial technical effects, specifically:

[0034] 1) When a visually impaired person is crossing a pedestrian crossing, a voice announcement device is used to make the visually impaired person aware that he or she is in the pedestrian crossing area and to inform him or her of the corresponding measures to ensure the personal safety of the visually impaired person when crossing the pedestrian crossing;

[0035] 2) The facilities for assisting the visually impaired to cross the crosswalk can intelligently screen out the visually impaired and track them in real time. When a visually impaired person crosses the crosswalk, the oncoming vehicle will be informed in advance so that the driver can slow down or stop the vehicle in advance. Furthermore, it can also solve the problem that the driver cannot immediately find the pedestrian crossing the crosswalk due to poor lighting at night, poor road visibility, or bad weather;

[0036] 3) It has realized the technological transformation from "human defense" to "technical defense", which not only meets the problem of visually impaired people crossing the crosswalk safely, but can also be widely used in crosswalk scenes with poor sight distance when crossing the street. "Technical defense" is used to make up for human visual defects, and the safety of crosswalks can be guaranteed even in conditions of poor sight distance such as bad weather.

[0037] Here, it is also necessary to explain that in the process of binary thresholding, two adjacent small-distance pixels in the thermal image frame are merged into a cluster, and the cluster is set with a point maximum lower limit. In this way, while ensuring the quality and accuracy of thermal image imaging, the data budget is reduced as much as possible, thereby shortening the calculation time of the data processing terminal.

[0038] Furthermore, the color change process of the signal traffic light is controlled by the data processing terminal, so that it can be intelligently adjusted according to the specific traffic conditions of the crosswalk, thereby ensuring that the visually impaired have sufficient time to cross the crosswalk. 车 ≥T 车 *V 人 In this case, the traffic light remains at a red light until the visually impaired person completely crosses the crosswalk, thereby effectively avoiding the phenomenon that a very small number of drivers endanger the personal safety of the visually impaired by rushing ahead.

[0039] It is known that according to common knowledge, a variety of methods can be used to achieve parameter calibration of 360° thermal imaging gimbal and laser radar. However, an implementation scheme with small total amount of data calculation, high imaging quality and very little noise is recommended. Specifically, in step S2, the thermal image is taken in a two-dimensional coordinate system [u 人 , v 人 ]T for calibration, and the radar point cloud image adopts a two-dimensional coordinate system [u 车 , v 车 ]T is calibrated; assuming that the resolution of the thermal image is A, then A = L × Q, where L is the number of pixels in the height direction and Q is the number of pixels in the horizontal direction. The images collected by the 360° thermal imaging gimbal are processed by morphological filtering and threshold segmentation in sequence to obtain binary images. The center of the 360° thermal imaging gimbal is used as the coordinate origin to establish an image coordinate system, and the binary image is placed in the image coordinate system. The binary image is traversed to determine the specific position of the visually impaired person.

[0040] Furthermore, as a further optimization of the above technical solution, the facilities for assisting the visually impaired to cross the crosswalk also include intelligent sensing electronic devices. The intelligent sensing electronic devices interact with the data processing terminal, and are carried or worn by the visually impaired. When the visually impaired are about to cross the crosswalk, the radio frequency identification devices located at both ends of the crosswalk can accurately identify the visually impaired and send real-time data to the data processing terminal immediately. Then, the intelligent sensing electronic device will issue a sound prompt to remind the visually impaired that they are about to cross the crosswalk. At the same time, the road warning screen and the voice broadcasting device are linked to display reminder subtitles and play voice prompts to remind passing vehicles to stop and yield.

[0041] Finally, it should be noted that the facilities for assisting the visually impaired to cross the crosswalk also include embedded solar road studs. Multiple embedded solar road studs are arranged in a linear array on one side of the crosswalk, and do not extend beyond the road surface after installation. When the 360° thermal imaging gimbal or intelligent sensing electronic device detects and senses that the visually impaired are about to cross the crosswalk, the data processing terminal sends a control signal to the embedded solar road studs, and the lights of each embedded solar road stud change color or flash to form a visual barrier on one side of the crosswalk to remind the driver to pay attention to the visually impaired who are walking slowly across the crosswalk at this moment.

[0042] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range of convergences with the principles and novel features disclosed herein.

Claims

1. A method for assisting visually impaired persons to cross a pedestrian crossing, which is implemented by means of facilities for assisting visually impaired persons to cross a pedestrian crossing, and is characterized in that: The facilities for assisting the visually impaired to cross the crosswalk include a monitoring pole, a 360° thermal imaging PTZ, a laser radar, a data processing terminal, a road warning screen and a voice broadcasting device; the monitoring pole is erected on one side of the crosswalk, and its cantilever beam crosses the crosswalk; the 360° thermal imaging PTZ is installed on the cantilever beam of the monitoring pole, and it is aligned with the center position of the crosswalk; a plurality of laser radars are installed on the cantilever beam of the monitoring pole and are linearly evenly distributed along its length; the road warning screen and the voice broadcasting device are both installed on the cantilever beam of the monitoring pole The data processing terminal is used to receive the real-time motion data collected by the 360° thermal imaging gimbal and the laser radar; under the control signal sent by the data processing terminal, the road warning screen can use real-time display text content to remind the driver to pay attention to the visually impaired person slowly walking through the crosswalk area, and the voice broadcasting device can use real-time voice broadcasting content to remind the driver to pay attention to the visually impaired person slowly walking through the crosswalk area, and the visually impaired person can know that he is in the crosswalk area by receiving the voice broadcast content; The method for assisting the visually impaired to cross a pedestrian crossing comprises the following steps: S1. Using the 360° thermal imaging gimbal to perform thermal imaging on pedestrians crossing the crosswalk, and screening out visually impaired persons according to the speed curve, and transmitting the collected thermal images of the visually impaired persons to the data processing terminal in real time; using the laser radar to scan the moving vehicles, and transmitting the collected radar point cloud images to the data processing terminal in real time; S2, calibrating the parameters of the thermal image and the radar point cloud image, and adjusting the clock sources of the two to be unified and the timestamps to be consistent; S3, the data processing terminal determines the real-time specific position and moving speed V of the visually impaired person according to the thermal image 人 , and estimate the time T required for a visually impaired person to cross the crosswalk 人 , and the data processing terminal determines the real-time specific position and moving speed V of the vehicle according to the radar point cloud image 车 , and estimate the time T required for the vehicle to reach the crosswalk 车 ; S4, if T 车 >>T 人 , the vehicle passes normally; if not, the data processing terminal sends a control signal to the road warning screen and the voice broadcasting device.

2. The method for assisting visually impaired persons to cross a pedestrian crossing according to claim 1, characterized in that: In step S4, at T 车 Not much larger than T 人 In the case of 车 <T 车 *V 人 , the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "pedestrians stop and wait" in a scrolling manner, and the voice broadcast device repeatedly plays the "pedestrians stop and wait" prompt sound; after the vehicle passes the crosswalk, the data processing terminal again sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "pedestrians pass" in a scrolling manner, and the voice broadcast device repeatedly plays the "pedestrians pass" prompt sound; if L 车 ≥T 车 *V 人 , the vehicle stops passing, and the data processing terminal immediately sends a control signal to the road warning screen and the voice broadcast device, the road warning screen displays the text content "Vehicle Stop Waiting" in a scrolling manner, and the voice broadcast device repeatedly plays the "Vehicle Stop Waiting" prompt sound.

3. The method for assisting visually impaired persons to cross a pedestrian crossing according to claim 2, characterized in that: The light color change process of the signal traffic light is controlled by the data processing terminal; 车 ≥T 车 *V 人 In this case, the signal traffic light remains in the red light state until the visually impaired person completely crosses the crosswalk.

4. The method for assisting visually impaired persons to cross a crosswalk according to claim 1, characterized in that: In step S1, the thermal image is composed of a plurality of thermal image frames played in time sequence; the collected thermal image frames are subjected to binary threshold processing by means of the data processing terminal; In the process of performing the binary thresholding process, when the distance between two adjacent pixels in the thermal image frame is less than the set threshold A1, they are merged into a cluster, and the cluster is set with a point maximum lower limit.

5. The method for assisting visually impaired persons to cross a pedestrian crossing according to claim 4, characterized in that: In step S1, the thermal image generation process includes the following stages: the image collected by the 360° thermal imaging gimbal is processed by morphological filtering and threshold segmentation in sequence to obtain a binary image; the center of the 360° thermal imaging gimbal is used as the coordinate origin to establish an image coordinate system, and the binary image is placed in the image coordinate system, and the binary image is traversed to determine the specific position of the visually impaired person.

6. The method for assisting visually impaired persons to cross a pedestrian crossing according to claim 1, characterized in that: In step S2, the thermal image is taken in a two-dimensional coordinate system [u 人 , v 人 ]T is calibrated, and the radar point cloud image adopts a two-dimensional coordinate system [u 车 , v 车 ]T is calibrated; assuming that the resolution of the thermal image is A, then A=L×Q, where L is the number of pixels in the height direction and Q is the number of pixels in the horizontal direction.

7. The method for assisting the visually impaired to cross a pedestrian crossing according to any one of claims 1 to 6, characterized in that: The facilities for assisting the visually impaired to cross the pedestrian crossing also include an intelligent sensing electronic device; the intelligent sensing electronic device interacts with the data processing terminal and is carried or worn by the visually impaired.

8. The method for assisting the visually impaired to cross a pedestrian crossing according to any one of claims 1 to 6, characterized in that: The facilities for assisting the visually impaired to cross the pedestrian crossing also include embedded solar road studs; a plurality of the embedded solar road studs are arranged in a linear array on one side of the pedestrian crossing, and do not protrude from the road surface after being embedded.