Design/Build vs. Traditional Construction User Delay Modeling: An Evaluation of the Cost Effectiveness of Innovative Construction Methods for New Construction
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4. Conclusions

The results show various scenarios produce different outputs for various corridors. However, the general results for the entire area show that Scenario 18 is slightly better than the others. In general, one can say that all scenarios which assume two lanes on the reconstructed section of I-15 are comparable. These scenarios are significantly lower than those with only one open lane on the I-15 mainline during the reconstruction.

In respect to the addition of one lane on SR-126 between 450 N and 12th Street, the model estimates savings from 100 to 160 delay-hours per day, depending on the closures of the surrounding interchanges. With an average delay savings of 130 delay-hours per day, the model estimates that the addition of a new lane on the section of SR-126 between 450 N and 12th Street would save around US $878,800.00. This number assumes that constant daily savings of 130 delay-hours are worth US $13.00 per hour for 520 working days during the reconstruction period of two years. However, this number might be slightly overestimated because the model has shown a lack of ability to reproduce accurate saturation rates for the major arterials. This inaccuracy in estimating saturation rates comes from the nature and limitations of transportation planning models. The major limitation seems to be the model's inability to distribute traffic demand over all links in the real street network. The network used in the model, as in most transportation planning models in the world, consists of freeways, major and minor arterials, and collector roads. In addition, transportation planning models, like the WFRC's TP+ and UTL's VISUM model, rarely include signals in their modeling procedures. In order to account for the signalized intersections on the arterials, these models use reduced capacities on the arterial links. It seems that either these capacities are overly reduced by the WFRC or the demand on the links in the model's network is overestimated. For this reason, if saturation rates on the major arterials in Ogden area were converted to HCM LOS, these values would be much higher than values obtained from traffic operations (or signal optimization) software like SYNCHRO. Other results from the study are more or less comparable with the field observations.

References


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