3. Skid resistance is the friction developed to prevent a tire from sliding
along the pavement surface.
Lower when affected by water due to the phenomenon of hydroplaning
and contaminated by mud or loose detritus resulting from the day to
day usage.
Important safety factor - Inadequate skid resistance will lead to higher
rick of accidents.
6. According to BS 812
The Polished Stone Value of aggregate gives a measure
of resistance to the polishing action of vehicle tires under
conditions similar to those occurring on the surface of a
road.
The samples are first polished by the Accelerated
Polishing Machine. Then the British Pendulum tester is
use to measure the PSV.
7. Specimens before and after polished
14 chips of sample clamped around the
periphery of the 'road wheel’
2 phases of abrasion
The first phase is of abrasion by a corn
emery for three hours, and then 3 hours of
polishing with an emery flour
Road wheel
8. According to ASTM E303-93
The specimen is clamped into the holder in the same
direction it has been polished in the machine
The specimen and the slider are thoroughly wetted before
each reading
The mean value is reported as PSV
PSV over 50 is regarded as a High Skid Resistant
Aggregate, PSV over 65 is needed for particularly high
stressed sites, PSV over 70 for rick sites
Slider traverses a length of 76±0.5 mm
9. Micro-texture
British Pendulum tester
Feature on site measurement
Static (spot measurement) skid resistance test equipment operated
by hand
Does not measure the impact that macro-texture has on skid
resistance as vehicle speeds increase
Not suitable for large scale investigating
Cheap, portable and is suitable for site and incident investigation
10. According to ASTM E1911
Measure pavement surface friction as a
function of speed
A disc that is made to rotate horizontally at
a specified velocity before being lowered
onto a wet pavement to measure friction
The friction is measure by the resistance
between the test surface and spring-loaded
slider
Spring-loaded slider
11. Device Features (Saito et al. 1996)
Measurement can be made in a very short time
The device is designed to be compact and easy to handle
Coefficient of friction is reported as a function of speed at a
contact pressure similar to that of typical vehicles
The slider can be easily replaced onsite, allowing the friction
characteristics of different tire’s materials
12. According to ASTM E274
To take a measurement, the vehicle (or trailer) is brought to the desired
testing speed (typically 64 km/hr (40 mph))
Water is sprayed ahead of the test tire to create a wetted pavement
surface
The test tire braking system is then actuated to lock the test tire
The result is reported as a Skid Number (SN).
14. Skid Number Comments
< 30 Take measures to correct
≥ 30 Acceptable for low volume roads
31 - 34 Monitor pavement frequently
≥ 35 Acceptable for heavily traveled roads
Advantage
Most commonly use in U.S
Reality
Typical Skid Numbers (from Jayawickrama et al., 1996)
15. Popular choice for the routine (proactive) monitoring of road networks
The pavement is tested wet and the vehicles are fitted with large water
tanks
The test speed typically adopted is 50km/h (slip speed of 17km/h)
Expensive compared to other types of test equipment
16. Compact and lightweight; easy to operate
and to transport
Braked wheel, fixed slip design with drag
and load measured continuously
Can be towed at any of the standard
testing speeds up to 130 km/h; can also be
used in pushing mode
Simple on-site calibration takes only 10
minutes
Rapid and simple data acquisition and
presentation
17. Benefit
Reliable - Low cost, robust and easy to maintain
Durable - Excellent repeatability and reproducibility
Accurate - Readings unaffected by road curvature
Versatile - Suitable road and runway
Easy To Transport - Can be towed by a wide variety of vehicles
Efficient - 100 miles of testing with one tank of water
Correlated Data - E274 Locked Wheel Tester, British Pendulum Tester
and SCRIM
Data Integration - Standard and custom data integration into any
pavement management system (PMS)
High Resolution - One reading every 32 inches
18. Measurement of friction and texture
Wet or dry measurements
Summer and winter measuring capability
Reporting of the International Friction Index
(IFI)
Reporting of the peak friction
Single test wheel can be mounted to any
kind of host vehicle or trailer.
Relatively expensive compared to portable
tester and the grip tester
19. This methodology offers several
advantages over current methods
used in the practice
The aggregates on the sample tray
with marked grid points
The images of each sample are
automatically captured for the
analysis of angularity and texture
The results are showed on the
computer
(Masad, 2003)
Sample tray
20. Advantages
Analyze the shape of a wide range of aggregate types and sizes
Combining both the coarse and fine aggregate analysis into one
system
Distinct difference between angularity and texture; these properties
have different effects on performance
21. Developed in 2004-2006
Measurement of:
◦ Macro-texture in circular path
◦ Micro-texture in certain points of that path
Structure:
Rotating level
Micro camera
Adjustable mechanism
Lens + Extension ring
Converging cercal of two lasers
Built-in macro sensor
Optical precision bearer
Micro laser emitter
Translating level
27. Feature
This approach is chosen when the texture
depth probably too low (<0.3mm)
The surface is pre-wetted in 1 minute
The time required for water drop from
upper reference line to lower reference line
is recorded
Very short outflow time is indicative of
rough surface and vice versa
3 and 10 seconds are satisfactory for an
asphalt pavement surface
28. The replacement for sand path and
outflow meter
Larger quantity of valuable and less
expensive
Greatly reducing the safety and traffic
control problems
Report mean profiled depth (MPD)
29. According to ASTM E 2157
CT Meter uses a laser to
measure
Record mean texture depth
(MTD) and root mean squared
(RMD) for each measurement
Record date, temperature,
concrete surface moisture, and
concrete distress at test
location
30.
31. IFI is a harmonized value of Friction index to convert all
skid and texture measurement to a common scale.
Developed by PIARC
According to ASTM E1960
IFI consists of two parameters:
◦ F60 – the coefficient of Friction at slip speed at 60km/h (Skid)
◦ Sp - the speed constant related to the surface texture depth
(Texture)
32. F(s) is the measurement of skid resistance made by any
piece of equipment, operating with slip speed
A and B are constants, the values of which were
determined for each piece of skid resistance measuring
equipment
S = a slip speed
60
60 ( ) exp
P
S
F A B F s
S
−
= + × × ÷
33. Sp = the speed constant related to the texture
depth, Tx
PS a b Tx= + ×
a and b are constants relating to the texture depth
measurement equipment.
