What Is a Standard Mileage Rate?

The mileage grade coefficient refers to the ratio of the designed capacity of roads at all levels to the designed capacity of roads at standard grades. Used in road network planning to calculate the length and comprehensive density of road networks in the planning area.

The mileage grade coefficient refers to the ratio of the designed capacity of roads at all levels to the designed capacity of roads at standard grades. Used in road network planning to calculate the length and comprehensive density of road networks in the planning area.

Probable capacity refers to the maximum amount of traffic that the road can actually bear, and refers to the capacity obtained after various roads have been modified, deviating from the above ideal conditions. The calculation of possible traffic capacity is based on the basic traffic capacity, taking into account the actual terrain, roads and traffic conditions, determining its correction coefficient, and then multiplying this correction coefficient by the aforementioned basic traffic capacity to obtain the actual road and traffic in a certain environment Possible capacity under conditions.

Possible capacity is also called possible capacity. Under actual road and traffic conditions, the maximum number of vehicles that can pass through a section of the road per unit time. Based on basic capacity, the capacity is modified based on actual road and traffic conditions that are ideal.

Road capacity refers to the ability of road facilities to divert traffic flow. That is, the ability of road facilities to pass traffic quality points within a certain period of time (usually 15min or 1h) and under normal road, traffic, control, and operation quality requirements. The capacity is generally expressed in terms of veh / h (vehicles / hour) and pcu / h (equivalent standard minibus / hour). The basic unit is: pcu / h / ln (equivalent standard minibus / hour / lane). Capacity is essentially a measure of road load performance, which reflects both the maximum capacity of the road to clear traffic and the limit of the vehicle's ability to bear the road under the premise of specified characteristics.

Road capacity means the ability of the road to bear the passing of vehicles. When the actual traffic volume on the road is less than its capacity, the vehicles on the road are in a free driving state, the speed is high, the traffic density is small, the distribution of headway distance conforms to the negative exponential distribution, and the vehicle can overtake; when the actual traffic on the road When the amount of traffic is close to or equal to its capacity, vehicles on the road are tracked at a near-uniform speed. The phenomenon of convoy driving occurs, and the headway distribution is close to the average value. When the actual traffic volume on the road exceeds its capacity, the road is driven. The density of vehicles increases, the speed of vehicles decreases, and traffic jams and blockages occur. Therefore, during the highway planning and design phase, the capacity and service level of various highway facilities should be analyzed and evaluated.

The main factors affecting road capacity are road conditions, traffic conditions, and the external environment of traffic. Road conditions refer to the geometric composition of the road, such as the number of lanes, lane width, lateral width, line of sight, longitudinal slope, pavement conditions, and streetization conditions along the line; traffic conditions refer to the composition and distribution of vehicles for traffic flow Regular characteristics, such as the amount of traffic, mixed vehicle types, pedestrians, and non-motor vehicle interference; the external environment of traffic refers to natural conditions other than road traffic, such as terrain, features, landscapes, and climate along the route. The combination of these three factors directly affects driving speed and road capacity.

According to the characteristics of the vehicle's running status, the traffic capacity can be divided into: road capacity, intersection capacity, capacity under confluence and divergence, capacity interweaving operating capacity ^[1]

Think of a section of a road as a dam's gate. When the gate opens indefinitely, the water flows through in a saturated condition. This is equivalent to a lane group in a certain direction of the road always releasing a green light, then the capacity of the lane group is equal to its saturated flow rate, that is, c = s * N, where N is the number of lanes of the lane group. However, the dam gate opening time is limited, that is, the real capacity is a part of the saturated flow rate (green light time part). The ratio of this time is g / C, and the green light ratio is also called the green letter ratio, that is, the green light. Time accounts for the total period of time. Therefore, the saturated flow rate is the number of vehicles in an ideal state, and the capacity is the number of vehicles passing within a certain period of time under real conditions ^[2] .