Add or Modify Roadway Pavement Vehicle Interaction Information

Selecting the "Pavement Vehicle Interaction" tab on the "Add or Modify Roadway" dialog, will cause the PVI form to be displayed.

The Pavement Vehicle Interaction (PVI) module is based on the latest research and model from the Concrete Sustainability Hub at the Massachusetts Institute of Technology (MIT), "PVI Mechanistic Model Gen II", Dr. Arghavan Louhghalam, in collaboration with Mehdi Akbarian and Prof. Franz-Josef Ulm. December 2013 (http://cshub.mit.edu/). The calculated PVI is a function of roadway deflection and surface roughness, both of which depend on the make-up of the top layer of pavement on a given roadway surface. The model demonstrates the possible increase in vehicle fuel consumption and related effects associated with the pavement performance over time. It does this by contrasting the pavement’s roughness and deflection over time relative to a theoretical rigid and smooth roadway; thereby, focusing on the effect of the pavement’s performance not the life cycle vehicle effects. GEN II improves on the PVI model by accounting for the impact of temperature and vehicle speed on fuel consumption. Using average fuel consumption for passenger vehicles and trucks (AADT(T)), it then models the influence of progressive increases in roughness and deflection of the roadway’s top layer over time (between major rehabilitations) and interprets the calculated decline in performance as increased vehicle fuel use due to the pavement.

The upper table on the input form allows the user to input multiple time segments throughout the lifespan of the roadway, so he/she can adjust the base PVI values when the surface is changed, for example after texturization or an overlayment.

While PVI has been studied in a number of one off pavement reports, to our knowledge it has never been incorporated into a commercial software tool. Unlike the LCI data for materials, plant operation and construction, which have been studied at length and for which there is considerable literature, PVI is relatively new and represents a forecast or future state scenario. A scenario carries with it a degree of uncertainty that needs to be duly considered. Obviously, uncertainty would best be handled using a statistical probability approach to the calculation model and the underlying data; something that this tool does not offer. Hence, the Institute advises those using the results from this PVI module to always acknowledge this uncertainty when discussing or presenting these results. Moreover, we recommend that when using this module, users complete a sensitivity analysis and error on the side of reporting conservative results in any public representation of these results.

The user must enter several parameters, for each time segment, in order to calculate the PVI effects:

PVI Data

Average Traffic Speed:

PVI calculations are based on the speed of traffic for a specific roadway, enter that speed here.

Initial Year:

The initial year for each distinct time segment of the PVI calculation. After the first time segment, the initial year is automatically entered as the final year of the previous segment. Typical initial year values are between 0.5 and 1.0 [m/km] or equivalently 31.7 and 63.4 [in/mi] or equivalently 2.6 and 5.3 [ft/mi].

Final Year:

The final year for each distinct time segment of the PVI calculation. The final year of the final segment must be equal to or greater than 30 years (the default lifespan of the roadway). Although IRI can go beyond a value of 6.0 [m/km] or equivalently 380.2 [in/mi] or equivalently 31.7 [ft/mi] where the roadway is essentially unusable, values between 3.0 and 4.0 [m/km] or equivalanetly 190.1 and 253.4 [in/mi] or equivalently 15.8 and 21.1 [ft/mi] are typical for triggering a major rehabilitation rehabilitation activity.

Top Layer Elastic Modulus (MPa or MBar):

The Elastic Modulus (E) or Young's Modulus of the pavement layer, for each time segment. The Elastic Modulus can vary greatly with temperature, an average value throughout the year is recommended. If you have multiple lifts of more than one type of pavement, you must calculate an average Elastic Modulus for the entire pavement layer.

Asphalt Pavements typically have values between 5,000 and 10,000 MPa.
Concrete Pavements typically have values between 20,000 and 50,000 MPa.

Top Layer Thickness (mm or inches):

The thickness of the top pavement layer, for each time segment. This is the entire depth of the pavement layer, if for example, you have 3 lifts of asphalt pavement of 50mm each, you should enter 150mm here.

Top Layer Density (tonnes/m3 or Tons/yd3):

The model is based on the deflection on a 1.0m beam (actually a 1.0m x 1.0m (1.0m2) beam) as thick as the user defines, and the mass of this beam, in kg, is needed as an input for the deflection calculation. This mass can be calculated by multiplying the thickness in mm by the density of the material in the top layer in tonnes/m3. For example, a 200mm layer of pavement, with a density of 2.345 tonnes/m3 will have a Mass per Unit Length of 200mm x 2.345tonnes/m3 = 469.0kg (1.0m x 1.0m x 0.200m x 2.345tonnes/m3 x 1000kg/tonne). The user has already input the top layer thickness, so all you need to do here is input the density of the top layer (in tonnes/m3 or Tons/yd3), and the mass of the 1.0m beam will be calculated in the background. If you have multiple lifts of more than one type of pavement, you must calculate an average density for the entire pavement layer.

Sub Grade Layer Elastic Modulus (MPa or MBar):

The Elastic Modulus of the ground sub layer (below the granular layers). This is sometimes referred to as the California Bearing Ratio (CBR), but the input here is required in MPa or MBar.

Initial International Roughness Index (IRI) (m/km or ft.mi):

The IRI of the surface of the roadway, at the beginning of each time segment.

Final International Roughness Index (IRI) (m/km or ft.mi):

The IRI of the surface of the roadway, at the end of each time segment.

Vehicle Type Data

Annual Average Daily Traffic - AADT:: Enter the AADT for both trucks and light duty vehicles.
Average Annual Average Daily Traffic Growth (%):: Enter the expected average annual increase in AADT for both trucks and light duty vehicles.
The following fields are constant inputs to the model and are not editable by the user, they are displayed for informational purposes only:: Average Fuel Consumption (L/100km or mpg):; Tire Load (kN/m or lbf/ft):; Tire Contact Area (m2 or ft2):; Primary Fuel Source:; Number of Wheels:; Average Number of Axles:; Average Maximum Operating Weight:; Note:
The Average Fuel Consumption data was derived from the US Federal Highways Administration (FHWA) report found at the following URL: http://www.fhwa.dot.gov/policyinformation/statistics/2010/vm1.cfm. The fuel consumption is calculated for each FHWA vehicle class based on total distance travelled and total fuel consumed for all vehicles in each class across all roads travelled on. These average data are then summarized on the basis of two vehicle types (Trucks and Passenger Vehicles). The resulting nominal fuel consumption by vehicle type has not been correlated to vehicle speed which varies by roadway type - a data anomaly which remains to be addressed.

Buttons

Save to Library:: Click this button to save the current design to the roadway library. Any user library designs are available, along with the database designs, in the Scenario drop down list in the Survey section of this dialog and will be available in any new or existing projects.
Duplicate Button: Click the "Duplicate" button to create an exact duplicate of the current assembly. The duplicate assembly will be added to the current project. This button is only available when editing or viewing an assembly that has already been saved in the current project.
Delete Button: Click the "Delete" button to delete the current assembly from the current project. This button is only available when editing or viewing an assembly that has already been saved in the current project.
Help Button:: Click the "Help" button to open the Help pop-up window.
OK Button: Click the "OK" button to accept and save the current design settings and close this dialog.
Cancel Button: Click the "Cancel" button to discard the current assembly settings and close this dialog.