| Term | Definition |
|---|---|
| Off-street parking |
Parking in appropriate facilities off the street. Does not refer to illegal parking at the roadside
|
| Oil mist |
Type of pollution caused by air with oil particules.
|
| On-street parking |
Parking within the street area whether in designated parking places or not
|
| Open (face) shield |
The shield normally used in soft ground tunnelling.
|
| Open cut |
A trench excavated from the surface and left uncovered until completion of the work within.
|
| Open-cut tunnel |
A tunnel constructed by excavating a trench from the surface, building the structure within the trench, and then backfilling to restore the surface.
|
| Operating cost |
The periodic, on-going cost of a system, facility or object. Depending on specific usage, may be restricted only to costs when a facility is used
|
| Operator (equipment) |
The person with direct control of the equipment
|
| Operator (system) |
A company, agency or person responsible for operation of a system
|
| Options / Alternatives |
Different solutions which meet the same objectives
|
| Out-of-pocket costs |
Costs directly affecting the person considered
|
| Outbye |
Away from the working face toward the shaft or portal.
|
| Outfitting |
See Fitting Out
|
| Overbreak |
Excavation that occurs outside of the "B" line of a tunnel owing to the irregular pattern of rock breakage; the definition also describes concrete required to fill this overexcavated space in lined tunnels.
|
| Overburden |
Essentially the same as cover, the total depth of soil and/or rock overlying the tunnel crown. Distinguished from another common definition as the mantle of soil or loose material overlying bed rock.
|
| Overpass |
A structure including its approaches which allows one road to pass above another road (or an obstacle)
|
| Owner |
A company, agency or person controlling a system, facility or object.
|
