Report contains the following papers: TI: Gap acceptance in the freeway merging process. AU: Drew-DR; Lamotte-LR; Buhr-JH; Wattleworth-JA SO: Highway Research Record, Hwy Res Board. 1967. NT: No 208, pp 1-36, 18 FIG, 8 TAB, 23 REF PY: 1967 AB: The first phase of a 4-yr program on freeway merging was undertaken by the bureau of public roads to furnish more detailed information on the effect of geometric variables on merging of ramp traffic, to develop usable distributions of traffic variables for simulation programs, and to develop an optimum ramp metering and merging control system. Emphasis is on collection and collation of gap acceptance characteristics. The theoretical development of models and useful parameters for describing the merging process include the derivation of the forms of the mean and variance of the delay to a ramp vehicle in position to merge and the treatment of the variability of critical gaps and gap acceptance among drivers through the identification of the representative forms for both critical gap distributions and gap acceptance functions. Through application of individual record probit analyses, simple, statistically significant relationships between the percent gap acceptance and gap size are established. The characteristics of lags and gaps and single and multiple-entry merges are compared, as well as fast to slow moving merging vehicles. The probit analyses are generalized to establish a relationship between percent acceptance as the dependent variable and gap size and vehicular speed as the dependent variables. /author/. TI: The development and validation of a digital simulation model for design of freeway diamond interchanges. AU: Gafarian, A.V. Hayes, E. & Mosher Jr., W.W. SO: Highway Research Record, Hwy Res Board. 1967. NT: No 208, pp 37-78 PY: 1967 AB: A digital simulation model for design of diamond interchanges was developed and validated. Experiments were conducted using magnetic loop detectors as well as helicopter - mounted 35 and 70-mm movie cameras for data collection. TI: Operational effects of some entrance ramp geometrics on freeway merging. AU: Wattleworth-JA; Buhr-JH; Drew-DR; Gerig-F SO: Highway Research Record, Hwy Res Board. 1967. NT: No 208, pp 79-122, 30 FIG, 4 TAB, 16 REF PY: 1967 AB: Time-lapse, aerial photographs were taken at 29 entrance ramps in seven cities across the country and data from 23 of these entrance ramps are presented. The ramps had a wide range of geometrics, i.e., acceleration lane lengths 240 ft to 1,500 ft and convergence angles between 1 and 14 deg. The geometric elements for which the operational effects were most carefully evaluated are acceleration lane length, angle of convergence and ramp grade. Operational characteristics examined were speed of ramp vehicles at the ramp nose and at the merge point, change of speed of ramp vehicles between the ramp nose and the merge point, the relative speeds of vehicles at the ramp nose and at the merge point, the accepted gap number and the distribution of points of entry onto the freeway. All of these analyses were made during periods in which the freeway operating speed was in excess of 40 mph. Each of the variables, acceleration lane length, angle of convergence and ramp grade, were found to have a great effect on the merging operation. General conclusions regarding entrance ramp design are presented. /author/.
Abstract