A pothole is a pot-shaped depression in a road surface, [1] usually asphalt pavement, where traffic has removed broken pieces of the pavement. It is usually the result of water in the underlying soil structure and traffic passing over the affected area. Water first weakens the underlying soil; traffic then fatigues and breaks the poorly supported asphalt surface in the affected area. Continued traffic action ejects both asphalt and the underlying soil material to create a hole in the pavement. [2]
According to the US Army Corps of Engineers's Cold Regions Research and Engineering Laboratory, pothole formation requires two factors to be present at the same time: water and traffic. Water weakens the soil beneath the pavement while traffic applies the loads that stress the pavement past the breaking point. Potholes form progressively from fatigue of the road surface which can lead to a precursor failure pattern known as crocodile (or alligator) cracking. [3] Eventually, chunks of pavement between the fatigue cracks gradually work loose, and may then be plucked or forced out of the surface by continued wheel loads to create a pothole. [4]
In areas subject to freezing and thawing, frost heaving can damage a pavement and create openings for water to enter. In the spring, thaw of pavements accelerates this process when the thawing of upper portions of the soil structure in a pavement cannot drain past still-frozen lower layers, thus saturating the supporting soil and weakening it. [4]
Potholes can grow to several feet in width, though they usually only develop to depths of a few inches. If they become large enough, damage to tires, wheels, and vehicle suspensions is liable to occur. Serious road accidents can occur as a direct result, especially on those roads where vehicle speeds are greater. [4]
Potholes may result from four main causes: [4]
The following steps can be taken to avoid pothole formation in existing pavements: [4]
At-risk pavement are more often local roads with lower structural standards and more complicating factors, like underground utilities, than major arteries. Pavement condition monitoring can lead to timely preventive action. Surveys address pavement distresses, which both diminishes the strength of the asphalt layer and admits water into the pavement, and effective drainage of water from within and around the pavement structure. [4]
Drainage structures, including ditching and storm sewers are essential for removing water from pavements. Avoiding other risk factors with good construction includes well-draining base and sub-base soils that avoid frost action and promote drying of the soil structure. Adequate crowns promote drainage to the sides. Good crack control prevents water penetration into the pavement soil structure. [4]
Preventive maintenance adds maintaining pavement structural integrity with thickness and continuity to the mix of preventing water penetration and promoting water migration away from the roadway. [4]
Eaton, et al., advocate a permitting process for utility cuts with specifications that avoid loss of structural continuity of pavements and flaws or failures that allow water penetration. [4]
Some municipalities require contractors to install utility repair tags to identify responsible parties of the deteriorated patches. [5]
A US Air Force manual advocates semiannual inspection of pavement cracks with crack sealing commencing on cracks that exceed 6.4 millimetres (0.25 in) [6]
Pothole patching methods may be either temporary or semi-permanent. Temporary patching is reserved for weather conditions that are not favorable to a more permanent solution and usually uses a cold mix asphalt patching compound placed in an expedient manner to temporarily restore pavement smoothness. Semi-permanent patching uses more care in reconstructing the perimeter of the failed area to blend with the surrounding pavement and usually employs a hot-mix asphalt fill above replacement of appropriate base materials. [4]
The Federal Highway Administration (FHWA) offers an overview of best practices which includes several repair techniques; throw-and-roll, semi-permanent, spray injection, and edge seal. [2] The FHWA suggests the best patching techniques, at times other than winter, are spray injection, throw-and-roll, semi-permanent, or edge seal procedures. In winter, the throw-and-roll technique may be the only available option. The Council for Scientific and Industrial Research in South Africa offers similar methods for the repair of potholes. [7]
Asphaltic patch materials consist of a binder and aggregate that come in two broad categories, hot mix and cold mix. Hot mixes are used by some agencies, they are produced at local asphalt plants. [4] The FHWA manual cites three types of cold mixes, those produced by a local asphalt plant, either 1) using the available aggregate and binder or 2) according to specifications set by the agency that will use the mix. The third type is a proprietary cold mix, which is manufactured to an advertised standard. [2]
The FHWA manual [2] cites the throw-and-roll method as the most basic method, best used as a temporary repair under conditions when it is difficult to control the placement of material, such as winter-time. It consists of:
This method is widely used due to its simplicity and speed, especially as an expedient method when the material is placed under unfavorable conditions of water or temperature. It can also be employed at times when the pothole is dry and clean with more lasting results. [8] Eaton, et al., noted that the failure rate of expedient repairs is high and that they can cost as much as five times the cost of properly done repairs. They advocate this type of repair only when weather conditions prevent proper techniques. [4]
Researchers from the University of Minnesota Duluth have tested mixing asphalt with iron ore containing magnetite which is then heated using ferromagnetic resonance (using microwaves at a specific frequency) to heat the mixed asphalt. The mixture used a compound of between 1% and 2% magnetite. The group discovered that material could be heated for a patch to 100 °C (212 °F) in approximately ten minutes which then applied a more effective repair and drove out moisture which improved adhesion. [9]
The FHWA manual [2] cites the semi-permanent repair method as one of the best for repairing potholes, short of full-depth roadway replacement. It consists of:
While this repair procedure provides durable results, it requires more labor and is more equipment-intensive than the throw-and-roll or the spray-injection procedure.
The FHWA manual [2] cites the spray-injection procedure as an efficient alternative to semi-permanent repair. It requires specialized equipment, however. It consists of:
This procedure requires no compaction after the cover aggregate has been placed.
The FHWA manual [2] cites the edge seal method as an alternative to the above techniques. It consists of:
In this procedure, waiting for any water to dry may require a second visit to place the tack coat. The tack material prevents water from getting through the edge of the patch and helps bond the patch to the surrounding pavement.
An FHWA-sponsored study determined that the "throw-and-roll technique proved as effective as the semi-permanent procedure when the two procedures were compared directly, using similar materials". It also found the throw-and-roll procedure to be generally more cost-effective when using quality materials. It further found that spray-injection repairs were as effective as control patches, depending on the expertise of the equipment operator. [8]
The American Automobile Association estimated in the five years prior to 2016 that 16 million drivers in the United States have suffered damage from potholes to their vehicle including tire punctures, bent wheels, and damaged suspensions with a cost of $3 billion a year. In India, between 2015 and 2017, an average of 3,000 people per year were killed in accidents involving potholes. [10] Britain has estimated that the cost of fixing all roads with potholes in the country would cost £12 billion. [9]
Some jurisdictions offer websites or mobile apps for pothole-reporting. These allow citizens to report potholes and other road hazards, optionally including a photograph and GPS coordinates. [11] [12] It is estimated there are 55 million potholes in the United States. [13] The self-proclaimed pothole capital, Edmonton, Alberta, Canada reportedly spends $4.8 million on 450,000 potholes annually, as of 2015. [14]
India has historically lost over 3,000 people per year to accidents caused by potholes. [10] This situation has engendered citizen movement to address the problem. [15]
In the United Kingdom, more than half a million pot holes were reported in 2017, an increase of 44% on the 2015 figure. There are processes in place to report potholes at different levels of jurisdiction. The process for claiming compensation varies by jurisdiction. [16]
Potholes have been commented on both in various media.
Two artists, Jim Bachor of Chicago and Baadal Nanjundaswamy of Bangalore, India, have used artwork as a commentary on potholes by placing mosaics (depicting ice cream in various manifestations) [17] or sculpture (in the form of a crocodile) in potholes. [18] Elsewhere, activists in Russia used painted caricatures of local officials with their mouths as potholes, to show their anger about the poor state of the roads. [19] In Manchester, England, a graffiti artist painted images of penises around potholes, which often resulted in them being repaired within 48 hours. [20]
The Beatles song "A Day in the Life" references potholes. John Lennon wrote the song's final verse inspired by a Far & Near news brief, in the same 17 January edition of the Daily Mail that had inspired the first two verses. [21] Under the headline "The holes in our roads", the brief stated: "There are 4,000 holes in the road in Blackburn, Lancashire, or one twenty-sixth of a hole per person, according to a council survey. If Blackburn is typical, there are two million holes in Britain's roads and 300,000 in London." [22]
In the Seinfeld episode The Pothole, George discovers that he has lost his keys, including a commemorative Phil Rizzuto keychain that says "Holy Cow" when activated. He then retraces his steps, and returns to a street where he had jumped over a pothole, which is now filled in with asphalt. The "Holy Cow" phrase is heard when a car runs over it.
A road is a thoroughfare for the conveyance of traffic that mostly has an improved surface for use by vehicles and pedestrians. Unlike streets, whose primary function is to serve as public spaces, the main function of roads is transportation.
Highway engineering is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods. Highway engineering became prominent towards the latter half of the 20th century after World War II. Standards of highway engineering are continuously being improved. Highway engineers must take into account future traffic flows, design of highway intersections/interchanges, geometric alignment and design, highway pavement materials and design, structural design of pavement thickness, and pavement maintenance.
A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads or dirt roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic.
Asphalt concrete is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen, laid in layers, and compacted.
Macadam is a type of road construction pioneered by Scottish engineer John Loudon McAdam around 1820, in which crushed stone is placed in shallow, convex layers and compacted thoroughly. A binding layer of stone dust may form; it may also, after rolling, be covered with a cement or bituminous binder to keep dust and stones together. The method simplified what had been considered state-of-the-art at that point.
Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques for roads, parking lots, and pedestrian walkways. Permeable pavement surfaces may be composed of; pervious concrete, porous asphalt, paving stones, or interlocking pavers. Unlike traditional impervious paving materials such as concrete and asphalt, permeable paving systems allow stormwater to percolate and infiltrate through the pavement and into the aggregate layers and/or soil below. In addition to reducing surface runoff, permeable paving systems can trap suspended solids, thereby filtering pollutants from stormwater.
A gravel road is a type of unpaved road surfaced with gravel that has been brought to the site from a quarry or stream bed. Gravel roads are common in less-developed nations, and also in the rural areas of developed nations such as Canada and the United States. In New Zealand, and other Commonwealth countries, they may be known as metal roads. They may be referred to as "dirt roads" in common speech, but that term is used more for unimproved roads with no surface material added. If well constructed and maintained, a gravel road is an all-weather road.
In geotechnical engineering, soil compaction is the process in which stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water being displaced from between the soil grains, then consolidation, not compaction, has occurred. Normally, compaction is the result of heavy machinery compressing the soil, but it can also occur due to the passage of, for example, animal feet.
The pavement condition index (PCI) is a numerical index between 0 and 100, which is used to indicate the general condition of a pavement section. The PCI is widely used in transportation civil engineering and asset management, and many municipalities use it to measure the performance of their road infrastructure and their levels of service. It is a statistical measure and requires manual survey of the pavement. This index was originally developed by the United States Army Corps of Engineers as an airfield pavement rating system, but later modified for roadway pavements and standardized by the ASTM. The surveying processes and calculation methods have been documented and standardized by ASTM for both roads and airport pavements:
Pavement engineering is a branch of civil engineering that uses engineering techniques to design and maintain flexible (asphalt) and rigid (concrete) pavements. This includes streets and highways and involves knowledge of soils, hydraulics, and material properties. Pavement engineering involves new construction as well as rehabilitation and maintenance of existing pavements.
Chipseal is a pavement surface treatment that combines one or more layers of asphalt with one or more layers of fine aggregate. In the United States, chipseals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as asphaltic surface treatment. This type of surface has a variety of other names including tar-seal or tarseal, tar and chip, sprayed sealsurface dressing, or simply seal.
Stone mastic asphalt (SMA), also called stone-matrix asphalt, was developed in Germany in the 1960s with the first SMA pavements being placed in 1968 near Kiel. It provides a deformation-resistant, durable surfacing material, suitable for heavily trafficked roads. SMA has found use in Europe, Australia, the United States, and Canada as a durable asphalt surfacing option for residential streets and highways. SMA has a high coarse aggregate content that interlocks to form a stone skeleton that resists permanent deformation. The stone skeleton is filled with a mastic of bitumen and filler to which fibres are added to provide adequate stability of bitumen and to prevent drainage of binder during transport and placement. Typical SMA composition consists of 70−80% coarse aggregate, 8−12% filler, 6.0−7.0% binder, and 0.3 per cent fibre.
Maxwell Products, Inc. is a privately held, pavement maintenance products manufacturing company based in Salt Lake City, Utah. Founded in 1975 by brothers Ted and Delwyn Maxwell, Maxwell Products manufactures asphalt and concrete pavement preservation products, including Elastoflex crack and concrete joint sealant, NUVO premium crack and concrete joint sealant, GAP Mastic, and GAP Patch.
In civil engineering, concrete leveling is a procedure that attempts to correct an uneven concrete surface by altering the foundation that the surface sits upon. It is a cheaper alternative to having replacement concrete poured and is commonly performed at small businesses and private homes as well as at factories, warehouses, airports and on roads, highways and other infrastructure.
Road surface textures are deviations from a planar and smooth surface, affecting the vehicle/tyre interaction. Pavement texture is divided into: microtexture with wavelengths from 0 mm to 0.5 millimetres (0.020 in), macrotexture with wavelengths from 0.5 millimetres (0.020 in) to 50 millimetres (2.0 in) and megatexture with wavelengths from 50 millimetres (2.0 in) to 500 millimetres (20 in).
Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.
Crocodile cracking is a common type of distress in asphalt pavement. The following is more closely related to fatigue cracking which is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile. Cell sizes can vary in size up to 300 millimetres (12 in) across, but are typically less than 150 millimetres (5.9 in) across. Fatigue cracking is generally a loading failure, but numerous factors can contribute to it. It is often a sign of sub-base failure, poor drainage, or repeated over-loadings. It is important to prevent fatigue cracking, and repair as soon as possible, as advanced cases can be very costly to repair and can lead to formation of potholes or premature pavement failure.
Soil stabilizers and road recyclers are engineering vehicles that were once similar machines; however, they are now specialised pieces of road making machinery and have developed into different machines. Other terms that are sometimes used are: road profiler, road reclaimer, road miller, road planer and pavement profiler. They are used in the process of full depth recycling.
Pavement performance modeling or pavement deterioration modeling is the study of pavement deterioration throughout its life-cycle. The health of pavement is assessed using different performance indicators. Some of the most well-known performance indicators are Pavement Condition Index (PCI), International Roughness Index (IRI) and Present Serviceability Index (PSI), but sometimes a single distress such as rutting or the extent of crack is used. Among the most frequently used methods for pavement performance modeling are mechanistic models, mechanistic-empirical models, survival curves and Markov models. Recently, machine learning algorithms have been used for this purpose as well. Most studies on pavement performance modeling are based on IRI.
Utility repair tag is a plastic color-coded pavement marker embedded in the top surface of an asphalt utility cut restoration to identify the responsible party of that pavement repair or patch. The tag is not to be used for identification of an underground utility location.