Detailed Visual Inspection (DVI)
Introduction to Detailed Visual Inspection Surveys (DVI)
The Detailed Visual Inspection survey (DVI) is specifically designed to provide more detailed information to support and validate treatment decisions and scheme identification, complementing the data obtained from CVI surveys. It is particularly useful for conducting routine visual assessments in areas where a more detailed examination is required or when driven surveys are not feasible.
In the DVI survey, road sections are divided into sub-sections, which can be identified within the section based on their start or end chainage and length. Regardless of the construction type, the sub-sections within a section are typically of consistent length, usually 20 meters. However, for jointed concrete carriageways, sub-section lengths may vary along the carriageway to treat each bay (the length between transverse joints) as a separate sub-section. Variable sub-sections can also be employed for other pavement types, particularly in locations where there are long stretches of consistent defectiveness or non-defectiveness, offering potential benefits. Some commercial Data Capture Device (DCD) software packages allow defects to be collected individually, with automatic post-processing facilitating their aggregation and allocation to sub-sections.
A typical DVI survey is conducted by two surveyors on foot, although, where permitted by local health and safety guidelines, a single surveyor may perform the survey. Both team members participate in identifying present defects, but generally, one surveyor records defects on the DCD while the other measures defect dimensions using a measuring wheel (and tape as needed), as well as the section/sub-section length. It's important to note that due to the nature of a walked survey, productivity is lower compared to a CVI survey, with typical outputs ranging from 2 to 5 kilometers per day.
When recording Wheel Track Major Cracking on Bituminous carriageways, the affected lane length is documented. The maximum length that can be recorded depends on the chosen cross-section position method. For example, using simplified cross-section positions, a 20-meter sub-section on a single two-lane carriageway would have a total lane length of 40 meters. On the other hand, utilizing full cross-section positions, each lane would be individually considered, resulting in a total length of 20 meters per lane. A lane is deemed defective if either or both wheel tracks are affected by the crack.
Wheel track cracking DVI
When documenting Wheel Track Cracking during a DVI survey, it is important to consider the extent of major cracking not only within the wheel tracks but also across the entire carriageway. This means that any area already recorded as Wheel Track Major Cracking should also be included in the assessment of Whole Carriageway Major Cracking.
When encountering single wheel track cracks, it is assumed that the width of the crack covers half a meter. This measurement is utilized to determine the extent of Whole Carriageway Major Cracking, taking into account the overall area affected by the cracks across the entire width of the carriageway.
Incorporating Machine Collected Rutting into DVI Surveys
Introduction
Efficient and accurate data collection is crucial in the field of pavement management. When it comes to assessing wheel track rutting, a recommended approach is to utilize machine-based techniques. This article focuses on the integration of machine-collected rutting data into Detailed Visual Inspection (DVI) surveys, highlighting the creation of a specialized survey type known as Machine Collected Rutting for DVI (DRUT). Additionally, it explores the importance of selecting the appropriate rutting survey type and provides insights into measurement techniques and guidelines.
DRUT Surveys
An alternative approach to facilitate the use of machine-based measurements as an alternative to visual assessments of rutting, the DRUT survey type has been introduced. This survey type specifically targets a single externally created defect. When conducting an Automatic Pass, such as generating a Performance Indicator, it is essential to select the appropriate Rutting Survey type in conjunction with the associated visual survey type. Notably, the prevalence of SCANNER surveys has made SCANNER-accredited vehicles the likely choice for machine measurements of rut depth.
Guidelines for Creating DRUT Surveys
To ensure accurate and reliable DRUT surveys, the following guidelines should be followed:
Average Rut Depth Calculation: Calculate the average rut depth value in millimeters for 10-meter sub-sections. This calculation involves determining the mean of all readings within the 10-meter length. Each reading represents the average rut depth of the left and right wheel tracks (using full cross-section positions).
Measurement Techniques: Laser or ultrasonic techniques are acceptable for measuring rut depth. However, it is imperative to demonstrate that the equipment used is calibrated to an accuracy of +/- 2mm in recording and processing rut depressions. While the number of transverse readings taken along the road may vary, it is recommended to have at least one reading every 2 meters.
Conclusion
By incorporating machine-collected rutting data through the DRUT survey type and adhering to the recommended guidelines, DVI surveys can benefit from enhanced accuracy and efficiency in assessing wheel track rutting. Leveraging the advancements in machine-based techniques, such as SCANNER surveys, provides valuable insights into rut depth measurements. It is crucial to consult the SCANNER User Guide and Specification for further details. Implementing these guidelines ensures reliable data collection and supports effective decision-making for pavement management and maintenance planning.