TRAFFIC Linda Parsley Overview of Presentation n Traffic

TRAFFIC Linda Parsley

Overview of Presentation n Traffic data input n Traffic categories n Representative vehicles n Traffic composition n Traffic volumes and growth rates n Axle loading n Speed-flow type n Traffic flow pattern

Uses of traffic data in HDM-4 n pavement deterioration n vehicle operating costs n travel time n quantities of vehicle exhaust emissions n calculation of energy use n economic analysis

Location of input traffic data Definition of project details: n Road sections n Vehicle Fleet n Normal Traffic Specification of Alternatives: n Improvement standard Configuration

Traffic Categories n Normal traffic l n Diverted traffic l n Existing traffic and expected growth on the road both with and without the investment Traffic diverted to the road as a result of the investment Generated traffic l New traffic induced by the investment

Representative Vehicles n Purpose: l n to group vehicles with similar characteristics to simplify input Method of grouping: l l composite vehicle - average characteristics of vehicles within the group actual vehicle - actual characteristics of most common vehicle of the group

Vehicle Hierachy Three levels: n Categories l n Classes e. g. l n motorised and non-motorised traffic; passenger cars, trucks, buses, carts…. Types e. g. l small car, medium car, large car, Toyota Corolla, Mercedes Benz…. . .

Motorised traffic Category Class Type

Non-Motorised traffic Category Class Type

Volume, composition and growth rates n Volume - AADT for MT & NMT n Composition - representative vehicles (%) n Growth - for specified periods l Annual percentage increase % l Annual increment of AADT l Actual AADT for each section

Axle loading For each representative vehicle n Number of axles n Equivalent standard axles l n affects paved road deterioration Number of light vehicles (< 3. 5 tons) l affects deterioration of unsealed roads

Traffic Interactions

Traffic Interaction Modelling n n n HDM-III did not consider traffic interactions HDM-95 considered effects of traffic interactions on speeds but not on other VOC (fuel but only through speed reduction) HDM-4 expanded the HDM-95 approach to consider other VOC components

Traffic interactions n Passenger car space equivalence n Speed flow types n Traffic flow patterns

Equivalencies n Used to convert heterogeneous stream to equivalent homogeneous stream n Two types n l PCE/PCU: Passenger Car Equivalencies l PCSE: Passenger Car Space Equivalencies HDM-4 uses PCSE

Differences between PCU and PCSE n PCU/PCE l consider two factors: l space occupied by vehicle l speed effects l n used in highway capacity calculations PCSE (HDM-4) l l considers only space occupied speed effects considered separately through speed model

PCSE Length Space (m) Gap

HDM-4 Speed-Flow Model

Speed-flow model requirements n n Requires speeds l Free speed (calculated) l Snom - Speed at nominal capacity (calculated) l Sult - Speed at ultimate capacity Requires capacities l Q 0 - Volume where interactions affect speeds l Qnom - Nominal capacity l Qult - Ultimate capacity specified in Configuration

Types of Capacities n Nominal Capacity l l n the capacity where the traffic stream is travelling at a constant speed sustainable over long time periods Ultimate Capacity l maximum possible capacity before flow breaks down

Annual Distribution of Hourly Flows Flow Periods Peak Flow /hr Next to Peak Medium flow Next to Low Overnight Number of Hours in the Year

Non-Motorised Traffic

Impact of NMT n NMT affect l l Motorised traffic flow and speed Motorised traffic operating costs Impact is specified through a friction factor n NMT also affect l l Safety related costs Road maintenance costs these are not considered in HDM-4

Other effects on speeds n Impact of roadside activities - side friction n Impact of road widths as limiting speeds n Speed limits n Enforcement factor

Key differences from previous models n Unlimited number of representative vehicles n Effects of congestion on speed, fuel, tyres and maintenance costs n Non-motorised transport modelling

Location of input traffic data Definition of project details: n Road sections l n Vehicle Fleet l n AADT, speed factors, speed-flow type, traffic-flow type axle loads, PCSE, speed parameters Normal Traffic l composition, growth rates

Location of input traffic data Specification of Alternatives: n Improvement standard l Diverted traffic / generated traffic Configuration l speed flow types, traffic flow patterns

Summary n n Aimed to show where traffic data is required in HDM-4 and its relevance and impact in the model Included traffic interaction and speed estimation which leads to VOC and RUE