Description of Exhibit 2.3: STEAM 2.0 Speed Models

The STEAM 2.0 speed equations calculate congestion delay in hours per vehicle mile as follows:

Speed equals one over the quantity one over free flow speed plus delay in hours per vehicle mile. For certain values of the ratio of average weekday traffic to hourly capacity, delay equals c1, a constant, times x, the ratio of average weekday traffic to hourly capacity (AWDT/C) raised to the power c2, a constant, times the natural logarithm e raised to the product of the constant c3 and x. For freeways, c1 equals 2.39 times 10 to the minus 8 for daily travel, 2.35 times 10 to the minus 7 for peak travel and 1.13 times 10 to the minus 7 for off-peak travel. The constant c2 equals 3.75 for daily travel, 3.29 for peak travel and 2.52 for off-peak travel. C3 equals 0.287 for daily travel, 0.235 for peak travel and 0.259 for off-peak travel. For signalized arterials, c1 equals 5.62 times 10 to the minus 4 for daily travel, 8.44 times 10 to the minus 4 for peak travel and 4.35 times 10 to the minus 4 for off-peak travel. The constant C2 equals 0.862 for daily travel, 0.615 for peak travel and 0.937 for off-peak travel. The constant C2 equals 0.00739 for daily travel, 0.124 for peak travel and 0.00516 for off-peak travel. For freeways, STEAM 2.0 applies this delay equation for AWDT/C ratios up to the values of 10.5 for daily travel, 12.1 for peak period travel and 11.1 for off-peak travel. For signalized arterials, this delay equation applies to AWDT/C ratios up to 9.74 for daily travel, 9.62 for peak travel and 12.6 for off-peak travel.

When AWDT/C (x) ratios exceed these values, STEAM employs a second delay calculation. Delay in this case equals the constant c4 times the quantity 1 minus the constant c5 times x raised to the power of the constant c6 times the natural logarithm e raised to the power of the product of the constant c7 and x. For freeways, the constant c4 equals .05 for daily, peak and off-peak travel. The constant c5 equals 0.01494 for daily travel, 2.865 times 10 to the minus for for peak travel and 0.001058 for off-peak travel. The constant c6 equals 3.42 for daily travel, 7.0 for peak travel and 4.91 for off-peak travel. The constant c7 equals negative 0.372 for daily travel, negative 0.797 for peak travel and negative 0.449 for off-peak travel.

For signalized arterials, the constant c4 equals .05 for daily, peak and off-peak travel. The constant c5 equals 0.01494 for daily travel, 2.865 times 10 to the minus for for peak travel and 0.001058 for off-peak travel. The constant c6 equals 1.61 for daily travel, 3.8 for peak travel and 2.91 for off-peak travel. The constant c7 equals negative 0.372 for daily travel, negative 0.797 for peak travel and negative 0.449 for off-peak travel.