# Pavement Preservation

Pavement preservation is a network-level strategy of low-cost treatments, mainly preventive maintenance, that keep sound pavements in good condition longer.

- Canonical URL: https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/pavement-preservation/
- Last updated: 2026-11-01

Pavement preservation is a long-term, network-level strategy of applying cost-effective treatments, mainly preventive maintenance, to pavements that are still in good condition, so that they last longer, stay safe and meet road users' expectations. It aims to keep good roads good rather than waiting to repair failed ones.

## Definitions

Preservation, maintenance, rehabilitation and reconstruction overlap in everyday use. The Federal Highway Administration (FHWA) uses the following definitions:

- **Pavement preservation:** programs and activities employing a network-level, long-term strategy that enhances pavement performance by using an integrated, cost-effective set of practices that extend pavement life, improve safety and meet road user expectations.
- **Pavement rehabilitation:** structural enhancements that extend the service life of an existing pavement and/or improve its load-carrying capacity (see [Introduction to Rehabilitation](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/rehabilitation/introduction/)).
- **Pavement reconstruction:** replacement of the entire existing pavement structure by placing the equivalent or an increased pavement structure.

Maintenance is distinguished from rehabilitation because maintenance treatments do not significantly change the structural or load-carrying capacity of the pavement. FHWA divides maintenance into three categories:

- **Preventive maintenance:** a planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, and maintains or improves its functional condition without significantly increasing structural capacity.
- **Corrective maintenance:** activities performed in response to a deficiency that harms the safe, efficient operation of the facility and the future integrity of the pavement section.
- **Routine maintenance:** work planned and performed on a routine basis to maintain and preserve the condition of the system, or to respond to specific conditions and events and restore an adequate level of service.

Preventive maintenance is the largest part of most preservation programs. Other types of maintenance may or may not be counted as preservation.

The 2012 federal surface transportation act, Moving Ahead for Progress in the 21st Century (MAP-21)[^1], used the same definition of pavement preservation programs and activities. It listed pavement preservation among the purposes of the National Highway System, made preservation projects eligible for funding under the Act, and emphasized preservation in agency planning and asset management.

## Timing and Pavement Condition

Most preservation treatments work best on pavements that are structurally sound and show little or no [distress](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/introduction/). The aim is to keep a pavement in the condition it is already in.

![Preventive maintenance when a pavement is still in good condition (green arrow) is significantly less expensive than treatment after pavement deterioration has accelerated (red arrow).](https://pavementinteractive.org/wp-content/uploads/2013/05/newsletter-chart-graphic.jpg)

*Figure 1.* Preventive maintenance when a pavement is still in good condition (green arrow) is significantly less expensive than treatment after pavement deterioration has accelerated (red arrow).

The condition of a pavement over time generally follows a curve like the one above (see [Pavement Life Cycle](https://pavementinteractive.org/reference-desk/pavement-management/analysis/pavement-life-cycle/)). The further condition falls, the more expensive the treatment needed to bring it back. An inexpensive preventive treatment applied early may raise condition only slightly, but it can postpone or avoid a much more expensive treatment later. A [life-cycle cost analysis](https://pavementinteractive.org/reference-desk/pavement-management/analysis/life-cycle-cost-analysis/) will commonly show early treatment to be more cost-effective than waiting, which is why maintenance programs should not simply fix the worst roads first. [Pavement management systems](https://pavementinteractive.org/reference-desk/pavement-management/overview/pavement-management-systems/) are often used to estimate these curves and recommend when to apply treatments.

Pavements in poorer condition still need some care while resources are found to rehabilitate them. Corrective treatments such as [patching](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/hma-patching/) and [pothole](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/potholes/) repair, and joint or slab replacement on rigid pavements, keep them at a minimum standard in the meantime. Smaller activities such as cleaning roadside ditches and crack filling may be treated as routine maintenance.

Preservation also depends on the structure underneath. A surface treatment cannot last if defects in the underlying layers cause the distress to return, so preservation works best on pavements with a sound [structural design](https://pavementinteractive.org/reference-desk/design/structural-design/pavement-structure/). Designs such as [perpetual pavements](https://pavementinteractive.org/reference-desk/design/structural-design/perpetual-pavements/), combined with preservation of the surface, can give large increases in pavement life with lower maintenance and life-cycle costs.

## Preventive Treatments for Asphalt Pavements

Common preventive treatments for asphalt pavements are seals and thin overlays:

- **[Crack sealing](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/crack-seals/)** places an adhesive sealant, usually asphalt binder or [asphalt emulsion](https://pavementinteractive.org/reference-desk/materials/asphalt/emulsified-asphalt/), in individual cracks, normally ones that are not load-related, to keep out water and incompressible material. The crack is routed to clean it and form a sealant reservoir, and a backer rod may be used to keep the sealant from running to the bottom. Sealing (rather than filling) is recommended for working cracks, [reflection cracks](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/reflection-cracking/) and most [transverse cracks](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/transverse-cracking/). Rubber from ground tires can be added to the sealant for elasticity.
- **[Fog seals](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/fog-seals/)** are light applications of asphalt emulsion that renew a weathered or [raveled](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/raveling/) surface and seal small cracks and voids. They are less effective where distress is extensive.
- **[Slurry seals](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/slurry-seals/)** are mixtures of slow-setting emulsion and well-graded fine aggregate, sometimes with modifiers or mineral filler. They seal the surface, restore uniform texture and improve [skid resistance](https://pavementinteractive.org/reference-desk/pavement-management/pavement-evaluation/skid-resistance/) on pavements in good condition that are starting to age.
- **Sand seals** apply emulsion and then sand or fine aggregate separately rather than as a mixture. The sand is spread immediately, or after the emulsion breaks and then rolled with a pneumatic-tired roller. They mainly seal the surface and improve skid resistance.
- **Scrub seals** use the same materials as sand seals, but a broom is dragged over the emulsion to push it into cracks and voids, and again over the aggregate to force it into the emulsion. The scrubbing can fill cracks that would otherwise need individual sealing.
- **[Chip seals](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/bituminous-surface-treatments/)** spray a high-viscosity binder, usually emulsion, and then cover it with [uniformly graded](https://pavementinteractive.org/reference-desk/materials/aggregate/gradation-and-size/) coarse aggregate that is rolled to embed it. They improve friction and seal pavements with mild, non-load-related cracking, and can serve as the wearing course on low-volume roads. A double chip seal adds a second binder application and a second layer of aggregate about half the size of the first, for a harder, longer-lasting treatment. Rubberized binder may be used to reduce reflection cracking.
- **Sandwich seals** place coarse aggregate directly on the existing surface, then binder, then a second layer of aggregate. They may be considered for pavements with [bleeding](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/bleeding/) or flushing.
- **Cape seals** are a chip seal followed, within a few days or weeks, by a slurry seal. The slurry locks the chips in place and gives a new wearing surface that can handle more deterioration than either treatment alone, for pavements that have some distress but do not yet need an overlay.
- **[Thin overlays](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/non-structural-overlays/)** add a new wearing course without adding significant structural capacity.

The right treatment depends on climate, traffic, the age and condition of the pavement, and the service life wanted from the treatment. Treatments can be combined, for example crack sealing followed by a surface seal, and seals can be reapplied every few years as long as the pavement remains structurally sound. With proper design and attention to existing condition, seals can be used on roads of any traffic level, including high-volume roadways (TRB, 2011[^2]). Selection guidance is given by Hicks et al. (2000[^3]), and crack sealing practice by Yildirim et al. (2006[^4]). The timing of preventive treatments is the subject of NCHRP Report 523[^5].

## Remaining Service Interval

Agencies need to predict how long a pavement will last before it needs work in order to forecast, budget and plan. This has traditionally been expressed as **remaining service life** (RSL), the time until the pavement reaches an unacceptable condition. FHWA has endorsed replacing RSL with the **remaining service interval** (RSI): the time remaining until a defined construction treatment is needed (FHWA[^6]).

FHWA's reasons for the change include:

- RSL has been defined and interpreted in different ways, and design-stage assumptions about service life are not necessarily carried into pavement management;
- the as-constructed pavement's properties and performance matter more for management than the as-designed pavement, and RSL was often taken simply as the design period;
- it is odd to measure a system's life by a failure that can be corrected; and
- RSL thinking can unintentionally encourage "worst-first" programming, which raises costs.

RSI can describe several future events at once. A pavement might, for example, be expected to need a slurry seal in about 2 years, a thin asphalt overlay in about 6 years and reconstruction in about 15 years; each of those is its RSI for that category of treatment. This fits pavement management practice, which increasingly plans different treatments at different condition thresholds rather than around a single end-of-life event.

Like other pavement management methods, RSI depends on periodic [condition surveys](https://pavementinteractive.org/reference-desk/pavement-management/pavement-evaluation/pavement-condition-rating-systems/). Measurable condition allows agencies to set thresholds and trigger rules for each category of treatment, and the RSI for a treatment is effectively a prediction of the time until condition reaches its trigger. Pavement management software can compute these intervals from performance curves fitted to observed condition, and comparing how treatments actually perform lets an agency refine its intervals and treatment choices over time. FHWA has published implementation guidelines for RSI[^7].

## Summary

Pavement preservation applies inexpensive treatments early, while pavements are still sound, to extend their life at the lowest long-term cost. It depends on good structural design, a pavement management system that tracks condition and times treatments, and the capacity to make corrective repairs when they are needed.

## Sources

[^1]: United States Congress (2012). Moving Ahead for Progress in the 21st Century Act (MAP-21). United States Congress, Washington, D.C.
[^2]: Transportation Research Board (2011). Guidelines for the Preservation of High-Traffic-Volume Roadways. SHRP 2 Report S2-R26-RR-2. Transportation Research Board, Washington, D.C. http://onlinepubs.trb.org/onlinepubs/shrp2/SHRP2-S2-R26-RR-2.pdf
[^3]: Hicks, R.; Seeds, S.; Geshkin, D. (2000). Selecting a Preventive Maintenance Treatment for Flexible Pavements. Foundation for Pavement Preservation. http://www.wsdot.wa.gov/NR/rdonlyres/F27BCD0A-793C-48EF-A795-6C57136C4437/0/PavementPreservation.pdf
[^4]: Yildirim, Y.; Qatan, A.; Prozzi, J. (2006). Field Manual for Crack Sealing in Asphalt Pavements. Center for Transportation Research, The University of Texas at Austin. http://www.utexas.edu/research/ctr/pdf_reports/0_4061_P3.pdf
[^5]: National Cooperative Highway Research Program. Optimal Timing of Pavement Preventive Maintenance Treatment Applications. NCHRP Report 523. Transportation Research Board, Washington, D.C. http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_523.pdf
[^6]: Federal Highway Administration. Techbrief: Pavement Remaining Service Interval. Federal Highway Administration. http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/13039/13039.pdf
[^7]: Federal Highway Administration. Pavement Remaining Service Interval Implementation Guidelines. Federal Highway Administration. http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/13050/13050.pdf