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SCOF Testing - "NYC Subway Tile Test"
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VOSI - Voices of Safety International SCOF Testing - NYC Subway Tile Test


"NYC Subway Tile Test"

Based on recent news media coverage of persons slipping on newly installed ceramic tiles in the New York City subway, the writer contacted Mr. Seymour Portes, Metropolitan Transportation Authority program manager for station rehabilitation, and John Penta of Caeser Ceramics. Mr. Penta, the importer of the subject tiles which are manufactured in Italy, supplied the writer with 2 sets of 12" square by 1/2" thick ceramic tiles. Each set contained one of the newly installed tiles, and one of the proposed replacement tiles. The newly installed tile contains feldspar and is identified as "Orion" tile, while the proposed replacement tile does not contain feldspar, and is referred to as "Pegaso".

"Orion" Tile - Front & Back "Pegaso" Tile - Front & Back

The American Society for Testing & Materials International (ASTM) C1028 test method, the ceramic tile industry standard used for measuring static coefficient of friction (SCOF), was performed on both tiles by the SGS/USA Testing Co., Fairfield, NJ. 

The Voices of Safety International (VOSI) V41.21 - "Universal Specification Test Method for Slip Resistant Walkways, in the Field & Laboratory as Measured by a Drag Type Friction Tester" was performed on both tiles in the Technical Products Co. laboratory in N. Caldwell, NJ. 

The test results are summarized in the following tables:

Corrected SCOF Table

Model 80

ASTM
C1028

Leather

EVA

Neolite

Neolite

Surface Tested

Dry

Dry

Wet

Dry

Wet

Dry

Wet

Orion Tile with Feldspar

0.74

0.56

0.54

0.54

0.57

0.78

0.70

Pegaso Tile without Feldspar

0.69

0.54

0.52

0.51

0.41

0.76

0.67

Minimum Required
Standard Coefficient of Friction
(SCOF)

0.45

0.50

0.35

0.50

0.35

0.50

0.35

 

Traction Index Table

The Traction Index indicates the ratio of the test surface SCOF
to the minimum required SCOF. 

Model 80

ASTM
C1028

Leather

EVA

Neolite

Neolite

Surface Tested

Dry

Dry

Wet

Dry

Wet

Dry

Wet

Orion Tile with Feldspar

1.64

1.12

1.54

1.08

1.63

1.56

2.00

Pegaso Tile without Feldspar

1.53

1.08

1.49

1.02

1.17

1.52

1.91

 

Conclusions:

  1. Both subway tiles, with & without feldspar, are slip-resistant per VOSI V41.21.

  2. The original subway tile, the "Orion" tile with feldspar, is more slip-resistant than the proposed replacement tile, the "Pegaso" without feldspar.

  3. The ASTM C1028 test method indicates greater resistance than the VOSI test method because of the use of Neolite with a low contact pressure, and excessive time during tests compared with the VOSI test method. This ASTM standard should reference the more realistic VOSI V41.21 test method.

  4. There is no ASTM standard that defines slip-resistant footwear. Since the tiles are slip-resistant in the VOSI standards, it is assumed that the footwear worn by the people that slipped on the subway tiles was not slip-resistant. The VOSI standard V41.22 should be used to test the footwear of slip & fall victims, in addition to the surface they slipped on.

  5. ASTM Committee F13 on Safety and Traction for Footwear should adopt the V41.22 test method in order to utilize existing standards for determining whether footwear is "slip resistant".

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Created: 2002-12-01 Last Updated: 2003-09-09