Important Notes For Highway Engineering

written by: Engr Sami Ullah (www.civilglobal.com)

In this Article I will write the important notes for highway engineering.

Alignment — the route of the road, defined as a series of horizontal tangents and curves.

Adverse camber — where a road slopes towards the outside of a bend, increasing the likelihood that vehicles travelling at speed will skid or topple. Usually only a temporary situation during road maintenance.

All-weather road — Unpaved road that is constructed of a material that does not create mud during rainfall.

Banked turn

Camber or Crown — the slope of the road surface downwards away from the centre of the road, so that surface water can flow freely to the edge of the carriageway, or on bends angling of the surface to lean traffic ‘into the bend’ reducing the chance of a skid.

Cant — super elevation

Cross slope the slope of the pavement, expressed as units of rise per unit of run, or as a percentage.

Grade — longitudinal slope

Belisha beacon — an orange globe, lit at night, used to highlight a pedestrian crossing.

Bollard — Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width

Byway — Highway over which the public have a right to travel for vehicular and other kinds of traffic, but is used mainly as a footpath or bridleway

Bypass Road that avoids or “bypasses” a built-up area, town, or village

Bottleneck — Section of a road with a carrying capacity substantially below that of other sections of the same road

Botts’ dots — Non-reflective raised pavement marker used on roads

Cat’s eye — reflective raised pavement marker used on roads

Central reservation — On dual carriageway roads, including controlled-access highways, divided highways and many limited-access roads, the central reservation (British English), median (North American English), median strip (North American English and Australian English), neutral ground [Louisiana English] or central nature strip (Australian English) — Area that separates opposing lanes of traffic

Chicane — Sequence of tight serpentine curves (usually an S-shape curve or a bus stop)

Chip seal — Road surface composed of a thin layer of crushed stone ‘chips’ and asphalt emulsion. It seals the surface and protects it from weather, but provides no structural strength. It is cheaper than asphalt concrete or concrete. In the United States it is usually only used on low volume rural roads

Corniche — Road on the side of a cliff or mountain, with the ground rising on one side and falling away on the other

Curb (kerb) — A raised edge at the side of the roadway.

Curb extension — (also kerb extension, bulb-out, nib, elephant ear, curb bulge and blister) Traffic calming measure, intended to slow the speed of traffic and increase driver awareness, particularly in built-up and residential neighborhoods.

Drainage gradient

Farm-to-market road — a state road or county road that connects rural or agricultural areas to market towns.

Fork — (literally “fork in the road”) Type of intersection where a road splits

Green lane — (UK) Unsurfaced road, may be so infrequently used that vegetation colonises freely, hence ‘green’. Many green lanes are ancient routes that have existed for millennia.

Guide rail — Prevents vehicles from veering off the road into oncoming traffic, crashing against solid objects or falling from a road. Also called a guard rail or traffic barrier.

Gutter (UK) — a drainage channel usually at the edge of the road or along a median.

Interstate Highway System (United States) — System of Interstate and Defense Highways

Lay by (Pullout, pull-off) — A paved area beside a main road where cars can stop temporarily to let another car pass.

Loose chippings — the hazard of stone chippings that have come loose

Median — On dual carriageway roads, including controlled-access highways, divided highways and many limited-access roads, the central reservation (British English), median (North American English), median strip (North American English and Australian English), neutral ground [Louisiana English] or central nature strip (Australian English) — Area that separates opposing lanes of traffic

Mountain pass — a relatively low level route through a range of mountains

Milestone — one of a series of numbered markers placed along a road, often at regular intervals, showing the distance to destinations.

National Highway — Road built and maintained by a national authority.

Pavement — The road regarded as a geoconstruction. In the UK the term is road surface and the pavement is a pedestrian walkway alongside the road.

Pedestrian crossing — Designated point on a road where road marking or other means helps pedestrians cross safely

Pelican crossing — (officially Pelican crossing) (UK) a Pedestrian Light Controlled crossing.

Private highway — Highway owned and operated for profit by private industry

Private road — Road owned and maintained by a private individual, organization, or company rather than by a government

Profile — the vertical alignment of a road, expressed as a series of grades, connected by parabolic curves.

Public space — Place where anyone has a right to come without being excluded because of economic or social conditions

Ranch road — U.S. road that connects rural and agricultural areas to market towns

Road number — Often assigned to identify a stretch of public roads— often dependent on the type of road, with numbers differentiating between interstates, motorways, arterial thoroughfares, etc.

Road-traffic safety — Process to reduce the harm (deaths, injuries, and property damage) that result from vehicle crashes on public roads

Roadworks — Part or the entire road is occupied for work or maintenance

Roughness — Deviations from a true planar pavement surface, which affects vehicle suspension deflection, dynamic loading, ride quality, surface drainage and winter operations. Roughnesses have wavelengths ranging from 500 mm up to some 40 m. The upper limit may be as high as 350 m when considering motion sickness aspects; motion sickness is generated by motion with down to 0.1 Hz frequency; in an ambulance car driving 35 m/s (126 km/h), waves with up to 350 m will excite motion sickness.

Roundabout (UK) a road junction where typically three or more roads are joined by a circular section of road. Traffic ‘on the roundabout’ has priority over traffic on approach roads, unless indicated otherwise. In countries where traffic drives on the left the roundabout is travelled in a clockwise direction. Also known as an island in parts of the UK.

Shoulder (also hard shoulder) — A clear, level area to the side of the roadway available for stopping if needed.

State highway — Road numbered by the state, falling below numbered national highways (like U.S. Routes) in the hierarchy or a road maintained by the state, including nationally-numbered highways

Traffic — Pedestrians, ridden or herded animals, vehicles, bicycles, and other conveyances using any road for purposes of travel.[49]

Texture (roads) — Deviations from a true planar pavement surface, which affects the interaction between road and tire. Micro textures have wavelengths below 0.5 mm, Macro texture below 50 mm and Mega texture below 500 mm.

Traffic calming — Set of strategies used by urban planners and traffic engineers to slow down or reduce motor vehicle traffic, thereby improving safety for pedestrians and bicyclists and improving the environment for residents

Traffic island — (UK) a small raised area used to help define the traffic flow, which may also act as a refuge for pedestrians crossing the carriageway or a location for signs, barriers or lights—a synonym for roundabout in some parts of the UK

Traffic light — Also known as a traffic signal, stop light, stop-and-go lights—a signaling device at a road intersection, pedestrian crossing, or other location that assigns right of way to different approaches to an intersection

Zebra crossing (UK) — a pedestrian crossing marked by black and white stripes on the carriageway

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