Mailbox Hazard and Risk Assessment (FY 2011-AK/24)
PROBLEM STATEMENT
Mailboxes are the closest obstacle permitted next to the travel lanes, yet little is known about the actual crash history. Although the Federal Highway Administration (FHWA) and the Postal Service encourage the use of crashworthy mailboxes, in the State of Alaska mailboxes are treated as a right of the property owner, and do not require a permit. Without a permitting process the department does not have a formal program to review mailbox crashworthiness with property owners. The opportunity for affecting general improvement occurs during capital projects for shoulder widening and realignment. On those projects, the department removes existing mailboxes and installs approved mailbox supports at little or no expense to the property owner. At least one state’s DOT policy is to install all roadside mailboxes, thereby establishing and enforcing crashworthiness outside of project funding.
In order to prioritize and comply with the roadside safety needs, the current level of crash risk against mailboxes needs to be examined and compared with other roadside point obstacle such as signs, luminaires, utility poles, trees, guardrail end treatments, and other fixed objects. Proportions of injury/fatality crashes need to be calculated to evaluate whether policies for stricter control of the run-of-the-way would affect any outcomes. In addition, the state capability to maintain mailbox support crashworthiness as a priority through routine programs should be investigated.
BACKGROUND
Although mailboxes are the closest obstacle allowed to the travel lane, their current level of crash risk is unknown. Fitzpatrick et al. (1972) collected accident data from four states (Michigan, Missouri, Texas and Washington) for the year 1972 and found that accidents against mailboxes represent a significant percentage of total fixed-object collisions. The Wisconsin Transportation Bulletin (1993) reported that limited data available suggests that, yearly, 70 to 100 highway deaths in the USA are related to mailboxes. The Postal Service has set some standards for residential mailbox installation and maintenance, and the AASHTO guide gives recommendations for both mailbox location and support types use (USPS, 2010; AASHTO, 1994). Some states, however, do not require a permit for mailbox installation, thus the level of the device crashworthiness cannot be verified.
The Texas Transportation Institute (TTI) has been involved in various projects aimed at reducing the probability of injury when mailboxes are impacted by a vehicle. Already back in 1980, Ross et al. performed seven full-scale crash tests to evaluate the impact behavior of rural mailbox installation. Three tests (out of the seven performed) involved multiple boxes mounted on boards with wood-post supports, two tests considered single box installation with steel pipe and breakaway mechanism, and the last two tests involved steel-pipe, multiple box support in the shape of an inverted U. Test results encourage the use of breakaway devices which showed to allow for minimal vehicle damage and potential occupant injury. On the other side, wood posts as mailbox supports seemed to present a problem especially when installed on roadway sections with allowed speed vehicle higher than 40 mi/h (64.4 km/h). Concerns were directed to the brittle property of wood support under impact, which would fracture at bumper height and keep the upper part of the post connected to the mailbox to ultimately impact the windshield.
Later in 1984,TTI performed a test and evaluation of neighborhood mailboxes, which are typically twelve to sixteen boxes housed in a metal framework and supported by a single vertical post, attached to a concrete footing (Campise and Ross, 1984). A neighborhood mailbox was impacted with a 1978 Honda at 60 mph. The vehicle exhibited a violent rollover and thus, did not meet the criteria of NCHRP Report 230 (NCHRP Report 230, 1981).
In 1993, tests were conducted by TTI to evaluate the performance of a new universal bracket which was designed by the Texas Department of Transportation (TxDOT) to attach different sizes of mailbox to the support post (Ross et al., 1993a). Tests were evaluated according to NCHRP Report 230. Only size no. 2 mailbox supported by two 2 lb/ft (3 kg/m) steel winged channel supports met the required criteria for acceptable performance.
TTI (Mak and Menges, 1996) conducted evaluation tests on a swing-away mailbox support designed by the Minnesota Department of Transportation in accordance with the guidelines set by the 1985 American Association of State Highway and Transportation Officials (AASHTO) (AASHTO, 1985). The Minnesota swing-away mailbox resulted in successfully meeting the evaluation criteria for a single mailbox assembly required by NCHRP Report 350 (NCHRP Report 350, 1993b).
More recently, TTI conducted a study to evaluate temporary barrel-mounted mailboxes to be used in work zones (Bligh et al., 2000). A mailbox on a plastic drum was impacted head-on by a Geo Metro at 56.7 mi/h (91.3 km/h). Based on the NCHRP Report 350 guidelines, the temporary mailbox support performed acceptably, since the mailbox on plastic drum did not penetrate the occupant compartment and both the occupant risks and vehicle trajectory requirements were met.
In the same period, TTI evaluated the performance of molded plastic mailboxes on three different types of support posts, including a 4×4 wood, a 2 lb/ft U-channel, and a 3-inch diameter schedule 40 pipe (Bligh et al., 2001). The device met the NCHRP Report 350 requirements for all three support types. The 4×4 timber support, however, appeared to be the best alternative from a functional and impact performance standpoint, having resulted in the least amount of windshield damage to the test vehicle. A 4×4 wood support post was thus recommended by TTI researchers for use with molded plastic mailboxes.
OBJECTIVE
The first purpose of this research is to evaluate the risk presented by mailbox supports. The second goal is to identify state permitting requirements and enforcement policies as they relate to mailbox supports. The third objective is to provide agencies with a guidance for policy options to prioritize safety initiatives that may lead to reduction of risk and/or reduced crash severity.
BENEFITS
The information compiled from this research will enable policy makers to evaluate what policy changes may be optimal to affect a reduction of severe crashes.
PRODUCTS
TTI will generate a report providing with survey results on current state agencies permitting requirements and enforcement policies related to mailbox supports. In addition, the report will include guidance for policy options aimed at prioritizing safety initiatives for the reduction of mailbox supports risk and/or crash severity.
IMPLEMENTATION
Guidelines regarding use of appropriate crashworthy mailbox support devices and standards for placements and maintenance will be suggested as a new policy for Alaska Department of Transportation.
WORK PLAN
Task 1 –Assemble and analyze multi-state crash for mailbox-related crashes
The researcher will collect available multi-state crash and severity data for mailbox support-related crashes and compare it with other fixed objects roadside obstacle such as signs, luminaires, utility poles, trees and guardrail end treatments. Proportions of injury/fatality crashes will be calculated.
Task 2 –Identify permitting requirements and enforcement policies relating to mailbox supports
The researcher will conduct a multi-state survey addressed at identifying state permitting requirements and enforcement policies relating to mailbox supports. The survey will be addressed to state departments of transportation employees.
Task 3 –Provide guidance for policy options
The researcher will develop crash rates and investigate possible correlations with policy options. In addition, the researcher will provide guidance for policy options and for the potential impacts of implementing changes with the scope of reducing risk and/or crash severity.
Task 4 –Generate final report
The researcher will generate a final report of the findings from the crash data collection and from the outcomes of the survey. In addition, the report will include guidelines for policy options aimed at limiting crashes involving mailbox supports.
| TTI Research Supervisor: Chiara Silvestri, Ph.D. Texas Transportation Institute Texas A&M University System 3135 TAMU College Station, Texas 77843-3135 (979) 845-8971 c-silvestri@ttimail.tamu.edu |
Pooled Fund Technical Representative: Jeff C. Jeffers, P.E. Assistant State Traffic & Safety Engineering Alaska Department of Transportation and Public Facilities 3132 Channel Drive P.O. Box 112500 Juneau, AK 99801-7898 (907) 465-8962 jeff.jeffers@alaska.gov |
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AASHTO (1985). Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. American Association of State Highway and Transportation Officials, Washington, D.C.
AASHTO (1994). A Guide for Erecting Mailboxes on Highways. American Association of State Highway and Transportation Officials, Washington, D.C.
Bligh, P. R., D. L. Bullard, et al. (2000). Impact Performance Evaluation of Work Zone Traffic Control Devices. Report No. FHWA/TX-01/1792-2. Texas Transportation Institute, College Station, TX.
Bligh, P. R., W. L. Menges, et al. (2001). Testing and Evaluation of Molded Plastic Mailboxes. Report No. FHWA/TX-01/1792-6. Texas Transportation Institute, College Station, TX.
Washington Transportation Bulletin (1993). “Mailbox Safety.” Retrieved 15 December, 2010, from http://epdfiles.engr.wisc.edu/pdf_web_files/tic/bulletins/Bltn_014_Mailbox_Safety.pdf.
Campise, W. L. and E. R. Hayes (1984). Test and Evaluation of Neighborhood Mailbox. Report No. FHWA/TX-84/52 +343-2. Texas Transportation Institute, College Station, TX.
Fitzpatrick, J. F. (1974). The Law and Roadside Hazards. Charlottesville, VA, Michie Co.
Mak, K. K. and W. L. Menges (1996). Testing of State Roadside Safety Systems Volume VII: Appendix F – Crash Testing and Evaluation of the Minnesota Swing-a-Way Mailbox Support.
Report No. FHWA-RD-98-042. Texas Transportation Institute, College Station, TX.
Michie, J. D. (1981). Recommended Procedures for the Safety. Performance Evaluation of Highway Safety Appurtenances. NCHRP Report 230. Washington D.C.
Ross, H. E., K. C. Walker, et al. (1980). “The Rural Mailbox: A Little-Known Roadside Hazard.” Transportation Research Record(769): 4-12.
Ross, H. E., D. L. Bullard, et al. (1993a). Mailbox Bracket Crash Tests. Report No. TX-94/1945-2F. Texas Transportation Institute, College Station, TX.
Ross, H. E., D. L. Sicking, et al. (1993b). Recommended Procedures for the Safety Performance Evaluation of Highway Features. NCHRP Report 350. Washington D.C.
USPS (2010). “Residential Mailbox Standards.” Retrieved 15 December, 2010, from http://www.usps.com/receive/mailboxstandards.htm.
