An analysis of the I-90 ramp closure system in Minnesota found benefit-cost ratios ranging from 0.13:1 to 3:1 with varying estimates of crash and delay reductions.

Date Posted

10/09/2001

Minnesota, United States

Interstate 90: Minnesota,

United States

Identifier

2007-B00473

Documentation and Assessment of Mn/DOT Gate Operations

Summary Information

This report evaluates the Minnesota Department of Transportation (Mn/DOT) operational procedure for restricting highway access when driving conditions are unsafe. During severe snowstorms and major incidents, mainline gates divert traffic from highways and gates located on entrance ramps prohibit highway access. Generally, Mn/DOT personnel report to gate locations and activate warning signs with amber lights. Gate arms are then swung or lowered into place and gate arm lights are illuminated. Once gate arms are deployed, law enforcement personnel man gate locations for one to two hours.

In Fall 1998 and between March and August 1999, Mn/DOT's Office of Advanced Transportation Systems conducted analyses to document past procedures and to identify current operational issues associated with gate systems. A benefit-to-cost analysis compared potential savings to estimated costs, and a winter storm case study compared costs for clearing a gated highway section to costs for clearing a section without gates.

FINDINGS

The benefit-to-cost analysis focused on costs of the Interstate 90 gate system and associated benefits due to delay and accident reductions. The annual frequency of snow/ice related accidents and hourly volume data were used in the analysis. Total system costs were calculated assuming deployment costs of 159,700 dollars plus five percent operations and maintenance costs over 10 years. The potential range of benefits and benefit-to-cost ratios are shown in Table 1.

Table 1: Range of Interstate 90 Gate System Benefits/Costs

Potential Range of Benefits over 10 Years	Benefit-to-Cost Ratio
10% Reduction in Delay (Low Volume) + 0% Accident Reduction = $28,096	0.13
20% Reduction in Delay (High Volume) + 1% Accident Reduction = $168,981	0.76
20% Reduction in Delay (High Volume) + 2% Accident Reduction = $217,636	0.98
30% Reduction in Delay (Low Volume) + 3% Accident Reduction = $230,253	1.04
40% Reduction in Delay (High Volume) + 0% Accident Reduction = $240,651	1.09
40% Reduction in Delay (Low Volume) + 3% Accident Reduction = $258,350	1.17
20% Reduction in Delay (High Volume) + 3% Accident Reduction = $266,290	1.20
50% Reduction in Delay (Low Volume) + 4% Accident Reduction = $335,101	1.51
40% Reduction in Delay (High Volume) + 4% Accident Reduction = $435,270	1.97
70% Reduction in Delay (High Volume) + 5% Accident Reduction = $664,414	3.00