When should I Pave a Gravel Road?
Municipal officials often ask this question. Citizens occasionally ask as well. There
are several considerations:
The worst thing to do is simply pave a gravel road to eliminate
Spring mud or Summer dust!
Pros & Cons
Paved and unpaved roads each
have advantages. The following summary applies
to properly constructed and maintained roads.
- Carry all water off the surface
and into ditches
- Eliminate dust and Spring
- Accommodate heavy trucks and
- Provide a smoother and safer
- Have low construction and maintenance costs for very
low volume roads
- Keep vehicles at lower speeds
- Can usually be maintained and repaired within a municipal
highway department’s capabilities
Traffic Weights and Volumes
Traffic volume and weight directly affect road longevity. Several agencies recommend that roads with less that 50 average
daily traffic (ADT) be unpaved. For ADT from
50 to several hundred, it is recommend to apply some type of asphalt-paved
surface be used.
For unpaved roads over 50 ADT, road managers should consider
vehicle weights and past performance. If the
unpaved road is performing well (especially during the Spring thaw),
with reasonable maintenance costs, paving is rarely justified. They should, however, consider applying a dust suppressant,
which will also stabilize the road surface.
Safety and Design
Safety is a primary consideration in road design. Whether paved or unpaved, a safe road must have sight distances,
alignments, and lane widths adequate for the expected speeds. The
adequacy of present geometric features should be considered in the
paved vs. unpaved decision. If inadequate, the
cost and other impacts of reconstruction are factors. Although adequate for an unpaved road, geometric features
might be inadequate for a paved road, which is often subject to
It is likely the base and drainage of an
unpaved road will need improvement before paving. Gravel
road bases are usually thinner than paved. Gravel
surfaces and bases usually have too many fines to meet paved road
design standards. Also, more water will run
off a paved road, so drainage must be examined and perhaps modified.
Gravel roads require grading, shaping, and regular addition
of gravel. Dust control is often necessary. These costs increase significantly as traffic volume and
weights increase. These increasing costs are
factors in the above noted recommendations based on ADT.
Municipalities should still calculate relative
costs for each specific situation. Estimates
should be based on future traffic demands. The
geometric features described above will affect cost comparisons. Drainage needs for both unpaved and paved alternatives should
be included. Maintenance as well as construction
costs must be considered. Cost studies should
also consider whether the current maintenance efforts, and their
costs, are adequate.
Although politics will invariably influence decision, focusing
on traffic weights and volumes, safety design and relative costs
will provide an informed decision. For more
detail, contact the Center for a copy of a publication with the
Adapted from the NH T2 Center newsletter, “Road Business”
This page last updated on