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| 3M products, services and expertise help traffic professionals address sign retroreflectivity upgrades and maintenance for positive guidance and traffic safety. |
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Why Sign Enhancement now?
Sign enhancement is needed now to meet changing retroreflectivity standards, population characteristics and vehicle diversity.
Safer roads are possible with retroreflective signs designed to optimize headlamp illumination and accomodate the geometries, vehicle disparities and human factors that are today's driving environment. Leading retroreflective sheeting manufacturers such as 3M are taking the initiative to bring better sign technology to the road.
Estimate your needs. Use 3M life-cycle calculator to estimate your sign inventory and potential investment.
Retroreflectivity Standards are Being Instituted
Hear from an Expert (video)
Higher standards are being instituted to accommodate older drivers with improved sign visibility.
- New, 6-inch letter height and name legibility recommendations1 are developing
- The FHWA-published table of minimum retroreflectivity values prohibits use of engineer grade sheeting on warning signs, as well as the white copy of guide signs. This table (click here to view) may soon be included in the Manual of Uniform Traffic Control Devices pursuant to a pending federal regulation.
Retroreflectivity Change Outs Within 10 Years
Federally-mandated minimum sign retroreflectivity standards became final on January 22, 2008.
- Systematic processes are required to ensure that sign retroreflectivity is maintained at or above minimum levels
- According to the FHWA "Public agencies and officials that implement and follow a reasonable method in conformance with the national MUTCD would appear to be in a better position to successfully defend tort litigation involving improper sign retroreflectivity than jurisdictions that lack any method"
- All change outs should be made within 10 years
Older Drivers have Different Needs
Hear from an Expert (video)
Most current landmark studies assume an 85th percentile benchmark sign performance where 85 percent of all drivers are adequately served. Increasing traffic sign luminance using high-efficiency retroreflective traffic sheeting serves the typically older driver. It also provides peace of mind for other drivers, especially under non-ideal driving conditions like adverse weather, dirty headlamps, etc. In effect, the "design driver" of the near future is someone over 652
- Aging eyes require the higher contrast, luminance and preview time offered by high-performance retroreflective signs3, 4
- Older drivers are more susceptible to glare from oncoming headlights; visual acuity is 12 to 18 times worse than that of younger drivers5
- Design improvements that accommodate older drivers5 (larger sizes, widest possible observation angle of retroreflectance, etc.) can be funded through SAFETEA-LU provisions and are found in Section 1405 of the legislation
Headlight Performance has Changed
Since the mid 1990s, FHWA and highway safety officials have been concerned about headlamp performance relative to sign guidance. An FHWA-sponsored literature review and field study noted several motor vehicle models did not provide sufficient illumination toward mounted signs.
Since then the introduction of VOA (visually/optically aimed) headlamps have reduced prospects for better illumination. VOA lamps are of two types:
- VOR provides a sharp horizontal right-side cut-off of the beam
- VOL provides a corresponding left-side cut-off
VOA headlamps also have:
Compromised Illumination: 80% of late model vehicles are factory equipped with VOA headlamps. This allows beam patterns to be aimed and adjusted on a flat wall, however the sharp cutoffs compromise the illumination capabilities of installed highway signs.
Compromised Sign Performance: VOA lamps compromise retroreflective sheeting performance and reduce the visibility of the signs significantly7
- Visibility down reduced 53% on right shoulder
- Visibility reduced 42% on left shoulder
- Visibility reduced 28% overhead
- When compared to pre-1997 tungsten-halogen headlamps, the newest high-density discharge (HID) xenon and bi-xenon headlamps need additional retroreflective efficiency to maintain sign effectiveness.
Vehicle Diversity Affects Performance
The wide range of vehicle sizes on the road—from motorcycles and subcompacts to eighteen-wheelers produces a wide range of different observation angles.
Larger vehicles have a wider observation angle, returning less light from headlamp to reflective sign and back to the driver’s eyes. SUV (sport utility) and LTV (light truck) registrations are higher than any other vehicle.
For this reason, sign sheeting should accommodate this growing number of vehicles with higher observation angles. Retroreflective sheeting should deliver optimum performance by being capable of the widest possible angles (0.5 – 1.5 degrees).
Useful Links
1 Manual on Uniform Traffic Control Devices – Design Guidelines
2 Staplin, Guidelines and recommendations to accomodate older drivers and pedestrians (FHWA-RD-01-051, 2001)
3 Schieber, F., Kline, D. W. (1994). Age differences in the legibility of symbol highway signs as a function of luminance and glare level: A preliminary report. HFES Annual Meeting, Human Factors and Ergonomics Society.
4 Staplin, L., Lococo, K., Byington, S., and Harkey, D. (2001). Guidelines and recommendations to accommodate older drivers and pedestrians. Washington, D.C., FHWA-RD-01-051.
5 Brabyn, et al, 2001; Burg, 1966
6 http://www.tfhrc.gov/humanfac/01103/coverfront.htm#toc. FHWA Older Driver Handbook
7 Sivak, M, A first look at visually aimable (VOA) and harmonized low-beam headlamps (UMTRI-2000-1)
