Facet Technology - Road Sign Predictive ModelingFacet Technology Corp. has built sign sheeting predictive modeling software that more accurately predicts the life of in situ signs. The predictive model utilizes field information gathered on signs throughout the US since 2006. The installation dates of the signs in the Facet database are from as early as 1987.

Background

There are over 70,000,000 traffic signs in the US. The MUTCD has specified use guidelines and requirements for many of these signs. Starting in 2009 the MUTCD specified minimum retroreflectivity levels and approved ASTM sheeting types for many of these signs. In addition, the MUTCD specified approved methods for assessing these signs in accordance with FHWA.

Sign sheeting manufacturers (3M, Avery Dennison and Nippon Carbide) provide warranties for their prismatic sheeting that are typically 7/10 years (7 years for full replacement and 10 years for sheeting only replacement).

DOTs will typically align their sign replacement schedules with: 1) expected sign life based on manufacturer warranty, 2) sign assessment information determined by an MUTCD-approved assessment method, or 3) sign assessment information determined by a non-MUTCD-approved assessment method. Sign replacement programs based on one of these foundations will lead to the over-replacement of signs in the field.

Facet Technology Corp. has built sign sheeting predictive modeling software that more accurately predicts the life of in situ signs. The predictive model utilizes field information gathered on signs throughout the US since 2006. The installation dates of the signs in the Facet database are from as early as 1987.

The biggest contributing factor to a sign’s life is sign sheeting type. Facet has a patented system for sign and pavement marking assessment. The Facet system utilizes information collected from moving vehicles to determine ASTM sheeting type and sheeting manufacturer. Versions of this patented system have been utilized to perform more than 40 sign inventory projects.

The graph below (displaying RA versus sign life in years for six ASTM sheeting types) shows the predictive model sign life curves for green sheeting utilizing out-of-the-box retroreflectivity numbers for the various ASTM sheeting types. As the graph indicates, ASTM sheeting types III and IX remain compliant with the MUTCD minimum levels in excess of 30 years and ASTM types IV and VIII remain compliant in excess of 40 years. Sign replacement programs driven by information from manufacturers will lead to premature replacement of assets that are performing within the documented guidelines.

Sign graph

Based on extensive analysis of signs in the field throughout the US, Facet believes that Departments of Transportation should expect to replace around 3% of their signs per year based on appropriate sign sheeting assessment and the utilization of predictive modeling for scheduled sign replacements. For a jurisdiction with an estimated 300,000 signs under management, based on an average cost of $300 to replace a sign in the field, the following table shows the expected sign replacement cost utilizing life-cycle management and compares the yearly cost to other levels of replacement.

Baseline – 3%Estimate – 5%Estimate – 6%Estimate – 8%
Yearly Sign Replacement Costs$2,700,000$4,500,000$5,400,000$7,200,000
Difference From Baseline$1,800,000$2,700,000$4,500,000

The information from the table suggests that lowering the sign replacement rate jurisdiction-wide from 6% to 3% would yield an annual cost savings of $2.7 million.