RESEARCH IN ECONOMIC ANALYSIS AT M.I.T.

THE PHOTOGRAMMETRY LABORATORY IS CONDUCTING A SERIES OF STUDIES AIMED AT THE INTEGRATION OF MODERN PHOTOGRAMMETRIC AND ELECTRONIC COMPUTING EQUIPMENT INTO AN EFFICIENT SYSTEM FOR THE LOCATION AND GEOMETRIC DESIGN OF HIGHWAYS. THIS LED TO THE DEVELOPMENT OF THE DIGITAL TERRAIN MODEL (DTM) SYSTEM AND A NUMBER OF ASSOCIATED INSTRUCTION PROGRAMS FOR AN IBM 650 ELECTRONIC COMPUTER. BASICALLY THE DTM SYSTEM INVOLVES THE COLLECTION OF TOPOGRAPHIC DATA IN DIGITAL RATHER THAN ANALOG OR MAP FORM. THESE DATA WHEN COMBINED PROPERLY WITH A MATHEMATICAL DESCRIPTION OF A TRIAL HIGHWAY ALIGNMENT CAN BE OPERATED UPON BY A COMPUTER SO AS TO PRODUCE COMPLETE INFORMATION ON THE GEOMETRY OF THE ALIGNMENT AND THE ASSOCIATED EARTHWORK QUANTITIES. ONE OUTGROWTH OF THIS EFFORT WAS THE DEVELOPMENT OF A METHOD OF ESTIMATING THE LAND COSTS ASSOCIATED WITH ALTERNATIVES IN ALIGNMENT. THIS METHOD INVOLVES MAKING AN APPROXIMATE ASSESMENT OF LAND COSTS, PROBABLY DIRECTLY FROM AERIAL PHOTOGRAPHS, FOR THE ENTIRE SECTION OF THE TERRAIN THROUGH WHICH ALTERNATIVE ALIGNMENTS FOR A HIGHWAY MIGHT BE EXPECTED TO PASS. THESE DATA, TOGETHER WITH A GEOMETRIC DESCRIPTION OF RIGHT-OF-WAY LIMITS AS DETERMINED BY THE DTM PROGRAMS ARE THEN FED INTO A COMPUTER WHICH OUTPUTS LAND COSTS FOR THAT ALIGNMENT BY STATION. A SECOND TECHNIQUE WAS DEVELOPED FOR COMPUTING VEHICLE OPERATING COSTS AND TRAVEL TIME REQUIREMENTS FOR ALTERNATIVE HIGHWAY ALIGNMENTS. CURRENT RESEARCH EFFORTS IN CONNECTION WITH THIS COMPUTER PROGRAM AND ITS USE ARE CENTERED AROUND 3 MAJOR PROBLEMS: (1) THE SIMPLIFICATION AND MODIFICATION OF EXISTING PROGRAM LOGIC SO AS TO PRODUCE ACCEPTABLE ANSWERS AT A SMALLER EXPENSE IN COMPUTER TIME, (2) THE SELECTION OF SAMPLE VEHICLES WHICH WILL BE TRULY REPRESENTATIVE OF A VERY LARGE AND DIVERSE FLEET OF VEHICLES WHICH CAN BE EXPECTED TO USE ANY HIGHWAY EVEN OVER AS LITTLE AS A YEAR'S TIME, AND (3) THE TESTING OF COMPUTED RESULTS TO DETERMINE HOW CLOSELY THEY WOULD CONFORM WITH ACTUAL VEHICLE PERFORMANCE. THE DISCUSSION BRINGS OUT THE VARIATIONS IN TERRAIN AND THE FACT THAT THE SYSTEM IS NOT ABLE TO TAKE ANY ACCOUNT OF CONGESTION. IT IS EMPHASIZED THAT THERE IS NO INTENTION OF TRYING TO COMPUTE BENEFIT-COST RATIOS OR RATES OF RETURN DIRECTLY.