This presentation was presented in Transportation Research Board 2019 conference at Washington D.C. In this study, an economic analysis was conducted to compare the cost of maintaining a gravel road to the cost of upgrading an existing gravel road to a double Otta seal surface. This analysis was conducted at three levels: (I) deterministic life-cycle cost analysis (LCCA), (II) a stochastic Monte Carlo simulation based LCCA, and (III) a traffic based economic analysis. A generic one-mile rural road in Midwest was considered as a case study location. Although, according to the analysis conducted in this paper, an upgrade to Otta seal investment might be justified by maintenance savings, resorting to only such justification cannot warrant investment in most cases. The upgrade from gravel road to Otta seal, or any other BSTs, might be justified in terms of enhancing safety for road users and also encouraging economic development beneficial to local areas.

1. Economics of Upgrading Gravel Roads
to Otta Seal Surface
Ali Nahvi, Yang Zhang, Ali Arabzadeh, Sharif Y. Gushgari, Halil Ceylan,
Charles T. Jahren, Douglas D. Gransberg, Sunghwan Kim
Dept. of Civil, Construction and Environmental Engineering (CCEE)
Program for Sustainable Pavement Engineering and Research (PROSPER)
Institute for Transportation (InTrans), Iowa State University (ISU)
98th TRB Annual Meeting
Washington D.C., January 13-17, 2019

2. Abstract
2
Maintenance of low volume roads especially gravel roads is costly, and
millions of funding annually are spent for aggregate replacement alone. Otta
seal, compared to other bituminous surface treatments (BSTs) for low volume
roads that require high-quality materials and specialized expertise, can be
constructed using cheaper local aggregates and accessible equipment.
However, only three states have reported Otta seal constructions and
performance in the US. In this study, an economic analysis was conducted to
compare the cost of maintaining a gravel road to the cost of upgrading an
existing gravel road to a double Otta seal surface. This analysis was conducted
at three levels: deterministic life-cycle cost analysis (LCCA), a stochastic
Monte Carlo simulation based LCCA, and a traffic based economic analysis. A
generic one-mile rural road in Midwest was considered as a case study
location. Although, according to the analysis conducted in this paper, an
upgrade to Otta seal investment might be justified by maintenance savings,
resorting to only such justification cannot warrant investment in most cases.
The upgrade from gravel road to Otta seal, or any other BSTs, might be
justified in terms of enhancing safety for road users and also encouraging
economic development beneficial to local areas.

3. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
3

4. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
4

5. Background
• Preventive pavement maintenance is defined as “a program strategy to
arrest light deterioration, retard progressive failures, and reduce the
need for routine maintenance and service activities” (FHWA 2007)
• Seal coatings are one relatively inexpensive type of treatment that can
provide a protective wearing surface on the existing surface to increase
service life
• An Otta seal is an asphalt surface treatment constructed by placing a
graded aggregate on top of a thick application of relatively soft
bituminous binding agent
5

6. Background
• The Norwegian road authorities desired that such a surface treatment
be cost-effective comply with the following requirements:
– Be cheap and easy to implement
– Utilize locally-available aggregates
– Be impervious to prevent water incursion into moisture-susceptible
base materials
– Be very flexible, durable, and easy to maintain
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7. Background
• This is related to lack of knowledge and the empirical design approach
associated with Otta seal, which requires evaluation of trial or
demonstration sections before deployment

8. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
8

9. Motivation and Objectives
• This study compares the life cycle cost of surfacing and maintaining
a gravel road with an upgraded gravel road to Otta seal coated
surface
• This study aims to provide a picture for local officials to decide at
what point it is desired to promote a gravel road to Otta seal coated
surface
• This study can be modified and used to address local conditions
9
Vs.

10. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
10

11. Approach/Methods
11

12. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
12

13. Cost Estimation (Cont’d)
• Gravel road
1 3 5
2 4 6
One-mile long road
The costs include
ongoing grading
activities and
regraveling every
five years
cost for the
motorgrader is 50
USD/hr
3 passes of the
motorgrader per
mile
Calculation of
motorgrader work
hours were based on
Caterpillar handbook
$$$$$
$$$$$
$$$$$
$$$$$
$ $ $ $
Year 0 Year 1 Year 2 Year 3 Year 4 Year 5
Gravel costs
$7.00/yd3

14. Cost Estimation (Cont’d)
• Otta seal
1 3 5
2 4 6
One-mile long road
Construction cost of
one-mile double
Otta seal was
obtained from bid
records
The annual average
maintenance for
bituminous roads
2,400 USD/mile)
Snow removal mile
driven cost (MNDOT
major highway
projects,2016)
Number of snow
events in were
obtained (ASOS
2018)
Two passes
snowplow for ice
and snow removal
Double chip seal Single chip seal Double Otta seal
Unitcost(USD/m
2
)
0
1
2
3
4
5
6
Unit cost range
(a) (b)

15. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
15

16. LCCA Framework
• The specific approach for this study utilizes equivalent uniform annual cost
(EUAC) analysis
• Twenty-year discount rate data from the Federal Reserve was obtained
and implemented into the model

17. LCCA Framework (Cont’d)
• Gravel roads
– Due to fluctuated number of grading operations, this variable treated
probabilistically in stochastic EUAC calculations
– Triangular distribution was used for gravelling, using three scenarios
developed based on discussion with Iowa and Minnesota county
engineers
Item
Low
value
Most likely
value
High
value
Number of grading operations
(during seven months)
21 50 70
Gravel road maintenance cost
(USD/ mile)
1,470 3,500 4,900
Double Otta seal cost (USD/mile) 57,000 59,800 67,600
Otta seal EUAC (USD/mile) 10,220 10,575 11,550
Gravel road EUAC (USD/mile) 5,500 7,530 8,930

18. LCCA Framework (Cont’d)
• Otta seal
– Similar to gravel roads EUAC calculations, maintenance was treated
deterministically for Otta seal LCCA analysis
– Based on the bid records from Minnesota, triangular distribution was
used to describe construction cost of double Otta seal
– Service life uncertainty creates sensitivity in EUAC results, making it a
good candidate for stochastic treatment

19. LCCA Framework (Cont’d)
• Stochastic analysis results
– Upgrading a one-mile gravel road to double Otta seal would require an
average of 2,400 USD in annual expenditures.
– Figure below also indicates that in nearly 20% of various possible
scenarios, surfacing a road with double Otta seal might incur the same
costs as those for gravel roads

20. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
20

21. Traffic Volume Based Economic Analysis
• Previous studies have shown that
annual maintenance cost for a gravel
road increases as the annual average
ADT increases
• Further studies needs to determine
the best times for upgrading gravel
roads to BST surfaces taking traffic
volume into consideration
• A detailed questionnaire was
developed for this purpose and sent
to some Minnesota and Iowa county
engineering offices
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(a)
(b)
(c)
Summary of interviews and surveys; (a) impact
of traffic on service life; (b) impact of traffic on
amount of required gravel for surfacing; (c)
impact of traffic on grading frequency

22. Traffic Volume Based Economic Analysis
• Gravel roads with high truck traffic and ADT over 200 are good gravel
road candidates for upgrading to Otta seal roads
22

23. Outline
• Background
• Motivation and Objectives
• Approach/Methods
• Cost Estimation
• LCCA Framework
• Traffic Volume Based Economic Analysis
• Indirect Benefits of Otta Seal over Gravel Road
23

24. Indirect Benefits of Otta Seal over Gravel Road
• It may not be possible to justify road way surface decision making
based solely on economic analysis
• There are many benefits associated with bituminous surface
treatments on an aggregate road that do not have monetary value
Increase in driving efficiency
Improve in living condition
Dust control
Higher skid resistance

25. Summary
• Stochastic and deterministic economic analyses were conducted to
determine needed investment to upgrade a gravel road to an Otta seal
road
• Historical bid and performance records of Otta seal in Iowa were not
available; therefore Minnesota was considered as a case study to conduct
the analysis
• Although the result of economic analysis reveals that in some cases an
upgrade to Otta seal investment might be justified by maintenance savings
alone, the analysis showed that the maintenance savings alone cannot be
a good justification for the investment for most cases
• However, the upgrade from gravel road to Otta seal, or any other BST,
could be justified to improve the quality of life for neighbors and the
safety of road users and to encourage economic development for the local
area benefit
• Local officials may use the cost estimating and the economic analysis
techniques described in this report to help them target investments
toward roads that will provide the best result
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26. 26
Thank you!
Any questions or
comments?