Street Repair Terminology
- Arterial streets
The most heavily used streets in the street system. Major arterials are usually four or more lanes, serve as major access routes to regional destinations, and carry an average of more than 20,000 vehicles per day. Minor arterials are usually two or three lanes in width, provide intra-city connectivity, and carry between 7,500 and 20,000 vehicles per day. Eugene has approximately 13.6 miles of major arterials and 67.5 miles of minor arterials.
- Collector streets
Streets that carry less traffic than arterials and provide access to neighborhoods and commercial and industrial areas. Major collectors typically carry between 2,500 and 7,000 vehicles, and neighborhood collectors typically carry between 1,500 and 2,500 vehicles per day. Eugene has approximately 33.9 miles of major collectors and 30.1 miles of neighborhood collectors.
- Local street
Streets whose primary function is to provide access to individual properties. Typically, they carry fewer than 1,500 vehicles per day. Eugene has approximately 383.9 miles of local or "neighborhood" streets.
Other System Terms
- Improved street
Streets constructed in accordance with the specifications established by the Eugene Public Works Department. Improved streets generally include engineered road beds and surfaces, storm drainage systems, sidewalks, street lighting and street trees. Approximately 88% of Eugene’s 530-mile street system is improved.
- Unimproved street
A street that is not constructed to City standards. Unimproved streets (and alleys) include gravel streets, oil mat streets, and streets that lack engineered road beds or drainage systems. Approximately 12% of Eugene’s 530-mile street system is unimproved, with most of the unimproved streets in the local or "neighborhood" street category.
- Travel lane
The portion of the street in which vehicles operate. Typically, travel lanes are 10 to 12 feet wide. The paved surface of the travel lane is called the driving course or top lift.
Street Condition Terms
The following terms are generally used to describe paving defects, ranging from least serious to most serious:
This is the first stage of street degradation, caused by weather (UV rays, oxidation, and expansion/contraction due to heating/cooling) and/or traffic (including wear from tires and studs). Fine particles are lost from the upper layer of asphaltic concrete, loose gravel may be present, and the surface appears rough.
This condition is typically caused by surface compression due to vehicle weight and motion. Cracks allow water to penetrate the surface, leading to more significant deterioration.
- "Alligator" cracking
When longitudinal and transverse cracks intersect, an advanced state of multi-directional cracking, sometimes called block or alligator cracking occurs. This is a precursor to the formation of potholes.
Usually caused by higher weight vehicles such as trucks and buses, which deflect the pavement surface and also can compress and distort the road base by "pumping" the underlying materials and creating subsurface voids.
If vehicle movement and/or water cause the top layer of asphalt to slough away and expose the subgrade or the road bed, the resultant condition is commonly called a pothole. Once the subgrade or road bed has been disturbed, the road is considered structurally failed.
Paving condition also can be described using rating matrices:
- Overall Condition Index (OCI) This is used to rate the condition of streets on a scale of 0 - "very poor" to 100 - "excellent".
- Pavement Management System
The computerized system used by the City of Eugene Public Works Department to record data and generate reports about the city’s streets and their condition.
Pavement Treatment Terms
Overall, street repairs tend to fall into two categories:
- Operations and Maintenance (O&M) The ongoing work efforts required to operate and maintain the transportation system. Examples include keeping the City’s traffic signals and street lights in good working condition, responding to neighborhood and citizen traffic issues, pothole patching, sweeping (a stormwater service), pruning street trees, painting pavement markings, replacing damaged signs, maintaining median strips, and providing the necessary technical, planning and administrative support required to provide these services.
The work done to preserve and extend the life of transportation system components. While maintenance work does protect road surfaces, the term "preservation" usually is applied to more extensive repairs such as rehabilitation and reconstruction.
Several techniques are used to repair streets, ranging from least expensive to most expensive:
- Crack sealing
The injection of hot tar or asphalt into cracks and paving seams.
- Slurry seal
A thin (usually 1/2 inch or less) application of liquid asphalt with a fine aggregate additive such as sand to fill surface voids.
- Chip seal
This technique uses an asphalt emulsion (liquid oil) into which rock chips are rolled to restore the driving course. Not currently used by the City of Eugene.
The application of a surface layer of asphalt or asphaltic concrete. An overlay may be a thin layer of material (usually 1 to 2 in inches thick and limited to travel lanes) or it may be a "full overlay" which typically is thicker in depth and usually runs from curb to curb in width.
Surface repairs to streets. Examples of rehabilitation work include slurry seals (on low-volume streets) and full paving overlays.
Extensive street repair work that typically involves the excavation of the existing street to the road bed and the rebuilding of the road bed and surface layers of the street. Reconstruction generally is at least four to five times more costly per lineal foot than rehabilitation.