5B-2-1 
CRACK SITUATION GRASP OF DIGITAL IMAGE METHOD 
Tatuhide NAKANE, Hisasi TAKAGI, Masaharu OZAWA 
Kokusai Kogyo Co., LTD. 
JAPAN 
mo31208@kkc.co.jp 
KEY WORDS: Crack, Laser, Optical detection sensor 
ABSTRACT 
Among a variety of damage phenomena that the pavement road shows, the crack of the road is the most remarkable. The influence that 
the crack exerts on the durability of the pavement road is extremely large. It is necessary to understand the damage situation of the crack 
in the maintenance control of the pavement road. 
The device that records the road image to understand the damage situation of the crack is developed. The record device is divided into an 
analog method and a digital method. Both can be installed in the vehicle and the road image is recorded at a speed of 80km per hour. A 
digital method scans the state of the road with a laser spot and an optical detection sensor. The laser spot rotates in the direction where 
the road is crossed at high speed and catches the change in an individual point in the reflection light amount with the optical detection 
sensor. Information caught with the optical detection sensor is recorded in the W-VHS videotape. When there is no crack in the road and 
the road is excellent, the reflection light amount increases and is recorded as information on a bright point. The crack exists in the road, 
and when the laser spot scans the crack, the reflection light amount decreases and is recorded as information on a dark point. The crack is 
recorded as if the shadow and can confirm the existence of the crack as a result. 
1 INTRODUCTION 
In the road extension of Japan, there are about 1,150,000km and 
75% is a pavement road (1998). Cost by which the road is 
maintaining controlled increases every year as the road extension 
increases. It is necessary to distribute the limited maintenance 
budget efficiently so that the country and the municipality may 
offer a safe, pleasant road service. Therefore, it is important that 
the road manager understands the damage situation on the surface 
of the pavement road to do an effective investment and reflect the 
result in the road mending. 
2 GRASP OF PAVEMENT DAMAGE 
The damage situation of the road is expressed by the crack, the rut, 
and roughness in Japan. To evaluate the use of the pavement 
quantitatively, Ministry of Construction developed maintenance 
control index (MCI) as an integrated evaluation value of three 
elements. Especially, the influence of the crack on the durability 
of the pavement road is extremely large. The road manager is 
confirming the crack situation by various means. 20 years or more 
ago was only a method of confirming the existence of the crack by 
eyes. This method takes time to understand the damage situation 
of a wide-ranging road and needs a large labor. Moreover, it is 
dangerous to confirm the crack on the crowded road. It is general 
to use the automatic measurement vehicle where a special record 
device was installed when the pavement damage of a wide- 
ranging road is understood now. As a result, a prompt, 
economical, safe pavement damage can be understood. 
3 AUTOMATIC MEASUREMENT DEVICE 
There are about 10 vehicles to investigate the damage situation of 
the pavement road in Japan. The system that automatically 
investigates the damage situation is installed in the vehicle. The 
item which this vehicle investigates is a crack, a rut, and 
roughness. The car equipped with the investigation system can 
run about 80km or less and acquire the damage situation of the 
road. Naturally, there is a big difference at the speed of the 
investigation when it is compared to execute the investigation as 
man walks and to execute the investigation by using the car. Most 
cars (system) cannot investigate in daytime and are executing the 
investigation at nighttime because the measurement technique is 
influenced by the sunlight. All cars are used to investigate an 
expressway and a general road. 
Figure 1- Road Damage Investigation Car