SUR 4201HW2BHorizontal Baseline Design
Assignment: Now we are to design a route baseline starting at the BP point and ending at the EP point. Here are the project requirements:
1. The first route tangent must be on the extension of the incoming pavement at the BP (no deflection for vehicle).
2. The last route tangent must be on the backward extension of the outgoing pavement at the EP.
3. All parts of the new route baseline must lie within the baseline corridor as mapped in HW1. (PIs may be outside).
4. You are to design a baseline were all horizontal curves have the same degree of curve D, an integer value.
5. Your baseline location and curves should allow for the highest possible speed of travel (minimize D.)
A typical baseline is shown: (note one PI is outside the baseline corridor, but all the actual baseline is inside)
Az 90 deg1
PI1
BP
10000N/2
10000E
Az 100 deg
PI
3Last EP
Process:
1. Extend the Begin Project reference bearing (Az) into the corridor. Select a design value of TTL1 (Total Tangent Length 1) to set the location of PI1. (Point of Intersection 1). Calculate the N/E Cartesian coordinates of PI1.
2. Extend the End Project reference bearing (Az) backward into the corridor. Select a design value for TTL(end) to set the location of PI(last). Calculate the N/E coordinates of PI(last).
3. Since our baseline will only have two PIs, you must calculate the second tangent's length and azimuth. After calculating it's azimuth, you must then calculate DELTA 1 and DELTA last from the azimuths.
4. To calculate the connecting Length and Azimuth of the TTL between PI1 and PI(last), use the distance formula between your PI1 Northing and Easting and PI(last) Northing and Easting for length. Calculate it's azimuth by: Az = atan ((Elast-E)/(Nlast-N). Calculate the two delta's at either end of this connecting TTL. You have now finished the tangent framework of the route. At each PI, you should have TTL length and azimuth coming in, delta, N, E.
5. Place horizontal curves at each PI by selecting a degree of curve (D) as integer values. Keep all curves the same degree. Iterate your design (even changing PI locations) to try to get the least degree of curve D while (1) not overlapping curves, (2) not overlapping the Begin or End Project points, or (3) not causing your baseline to go out of the baseline corridor.
6. Calculate curve data for each curve: R, T, L, LC, M, E
7. Station your alignment, assigning the Begin Project at station 10+00. Calculate stations for each curve's PC, PI, and PT, along with the End Project point.
8. Calculate the N/E cartesian coordinate of each PC and PT
Submit:
1. A single Excel file containing
(a) A text box where you "talk to me" with design thinking. Give a summary of your results and observations,
(b) your calculations including TTL data,, DELTAs, CURVE data, STATIONS, and CARTESIAN COORDS and
(c) an Excel chart of your cartesian coordinates. Correct the chart for minimum coordinates and aspect so it is a realistic plot of the baseline.