Descriptions of the Measures

The aim of this measure is to display the smoothness of the journeys experienced by road users. STE is the percent of travel on roads smoother than the threshold for each traffic grouping, reported by One Network Road Classification (ONRC) classification, for your network, Peer Group , Region and the Nation .

In 2018 the Te Ringa Maimoa Transport Excellence Partnership and Waka Kotahi determined that STE will be calculated solely on the basis of Road Sections. 

This report now calculates Smooth Travel Exposure (STE) by road section. The historical Treatment Length option is no longer available in Transport Insights.

The calculation determines smoothness using the Vehicle per Day bands currently implemented in RAMM, together with their NAASRA thresholds.

Calculating smooth lengths by Road Section

The Road Section calculation will locate the roughness (100m roughness and HSD) readings for all road section records in the network, and calculate the smooth length within each road section. The calculation will use the roughness (100m roughness / HSD) readings that have the latest reading dates.

If a roughness record overlaps more than one road section, the length of the roughness record will be apportioned to each road section it overlaps. For the purposes of the calculation, the roughness record will effectively be split on each road section boundary. When a roughness record is apportioned across multiple road sections, each road section-portion will retain the NAASRA value of the roughness record.

If there is no roughness (HSD or rough) record for a length within a road section, the calculation will record the length of the road section surveyed and the length smooth, using these figures to calculate the percentage smooth. It is anticipated that Road Controlling Authorities (RCAs) take roughness readings across their entire network every two years, and any gaps are presumed to be unreadable.

Once the smooth length and survey length have been calculated for each road section, STE percentages will be calculated using the sum of smooth lengths / sum of survey lengths, weighted by VKT.

The example shows how we allocate smooth travel to ONRC categories. 

In the example, the smooth travel is calculated per road section.  When the smooth travel is summed over all the road section(s) of Arterial classification the result is 1200m out of 1500m, giving an STE of 80% for the Arterial classification.  Likewise for primary collector, 800m of smooth travel out of 1000m is 80%.

VKT Weighting

The Vehicle Kilometres Travelled (VKT) for the Smooth portion of the {Road Section} is calculated from the apportioned STE using the formula: road section length/1000*traffic estimated volume*365.

Smooth Travel per classification is the sum for all roadways in the One Network Road Classification (ONRC) .

VKT per Classification is calculated from Road Section View and is calculated as the sum for road section(s) in the classification.

STE in the report is calculated as Smooth Travel per Classification / VKT per classification.

Historical calculation by Treatment Length

The historical STE report option used data summarised in the RAMM treatment length table, indicating the length of smooth road per Treatment Length as calculated by RAMM.