Horizontal Geometry (Alignment)

[CarbonFlora]

Checklist Portion Compliance

1.1 Design Speed

HDM Index 101.1 should be read before selecting a design speed.  Design speed selection will affect sight distance, vertical alignment, horizontal alignment, and other requirements.  Based on engineering judgement, projects with multiple roadways may require more than one selected design speed. 

Proposed design speed for project
Minimum Design Speed for this type of facility
Design Speed of the roadway segment prior to project
Design Speed of roadway segment after project
Posted speed (for existing facilities)
Operating speed (85th percentile or observed) (for existing facilities)
Does the design speed comply with Topic 101 including the parameters indicated in Index 101.1(2) and the ranges shown in Table 101.2? [B: Index 101.1, Index 101.2 and Table 101.2] and [U: Index 101.1]
If the selected design speed does not fall within the range shown in Table 101.2, has concurrence been received from the Project Delivery Coordinator, District Design Liaison and District traffic unit?
Does the design speed meet or exceed the posted and operating speeds?
Is design speed consistent with the Project Initiation Document (PID) or Project Report (PR)?  
Does the PDT concur with the selected design speed of the project?

2.2 Horizontal Alignment

1. Do all the curve radii exceed the minimum values listed in Tables 202.2A - 202.2E for the appropriate superelevation rate and design speed? [B: Index 203.2 and Tables 202.2A - 202.2E]
2. Is the minimum stopping sight distance listed in Table 201.1 provided at each horizontal curve for the appropriate design speed? [B: Index 203.1, Index 201.1 and Table 201.1]; (Also see Index 203.2 and Figure 201.6 if desired lateral clearance to an obstruction is not achievable)
3. If central angle is less than 10 degrees, is the curve length 800 feet or greater? (See Index 203.4)
4. Is the curve length on 2-lane roads between 500 feet and ½ mile? (See Index 203.4)
5. Where compound curves are necessary, is the shorter radius, R1, at least two-thirds the longer radius, R2 (when R1 < 1000 feet)?  On one-way roads does the larger radius follow the smaller radius? [U: Index 203.5]
6. Is the intervening tangent between horizontal reversing curves long enough to accommodate the standard superelevation runoffs given in Figure 202.5A? If not, is it at least long enough for the 6% maximum per 100 feet rate of change? ] When feasible, is at least 400 feet of tangent length provided? [U: Index 203.6 and Figure 202.5A]  
7. For local facilities, within the State R/W, with either no connection or a connection to a non-access controlled facility, does the horizontal alignment conform to AASHTO standards? [B: Index 203.1] If local agency standards are applied, do those standards exceed AASHTO standards? [U: Index 203.1]
8. For freeways, are 5000-foot and 3000-foot minimum radius curves used on the mainline in rural and urban areas respectively? (See Index 203.2)

Addendum 1 (Jasper)

For design, I need the info for the following ASAP:

1. # of lanes that could fit at the ramp terminals. Meaning how many turn lanes can fit when connecting with the local road. As well as how long the lanes can be.
2. If it is feasible to put 2 on-ramp lanes to accommodate ramp metering.

Figure 1: Details on what Jasper wants from this task

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Co-requisite

This task is to done in conjunction with issue #37

Brief

Corridors require control lines to describe the horizontal geometry. Whatever design decision you make, write it down with it's corresponding reference. This is referred to as documentation and it's purpose is for you to defend your decisions. Non-standard features are allowed, but you need a damn good reason to do so. The following is an example excerpt you can use as a guide:

## Details 
### Design Speed
According to HDM 504.2.4.a, "Freeway Exit—The design speed at the exit nose should be 50 miles per hour or greater for both ramps and branch connections."
    Therefore, the inital design speed is 50mph.

According to HDM 504.3.1.a, "An acceptable approach is to set design speeds of 25 miles per hour and 50 miles per hour at the ramp terminus and exit nose."
    Therefore, the ramp design speed is 50 up to the first curve, linearly decelerating, down to 25mph.

The following are the criteria you should have documented by the end of this task:

1. Design Speed of all proposed segments. This includes the design speeds at the beginning and terminus of ramps. Design speed for ramps range from 50-25mph if I recall correctly.
2. Control line curve radii & inner-most lane curve radii. The inner-most lane curve radii must not be smaller than your calculated minimum.
3. Shoulder widths on roads & shoulders. Since we are accommodating for trucks, your ramp shoulders will vary!
4. Sight distance checks at intersections & roads. On ramps, your middle ordinate is only the shoulder + 1/2 of a lane. You will realize this is the primary criteria for ramp radii.
5. From [Addendum 1], max # of lanes that could fit at the ramp terminals (end). Also give their maximum length.
6. From [Addendum 1], Boolean value if it is feasible to put 2 on-ramp lanes for every instance of an on-ramp.

See the following document for diagrams on some horizontal design standards: https://github.com/CarbonFlora/senior_project/blob/master/HA_control_lines.md

Preliminary Knowledge

The Caltrans office can be removed. Local streets not connected to anything can terminate after 200ft.

Save the files here: 2023-2024 I-10 Project\06 - Joint Design Teams\02 - Design Team 2 (Zi)\[first_name]

Remember

• Document your decision making process and assumptions. This will be helpful for the PDT meeting slides. One of the purposes of the PDT meeting is for others to constructively criticize your work and ideas.
• Check your horizontal alignment against section 2.2 of the checklist.
• https://github.com/CarbonFlora/senior_project/blob/master/checklist.md#22horizontal-alignment
• The control line for ramps is on the edge of the lane.
• The tools you may be using are the line and arc tools in ORD. Remember to add alignment labels.
• Try adhering to the HDM for minimum curve radius and overall exit/on ramp geometry.

[dschhen]

Design speeds, control line curve radii, shoulder widths

• The three parameters above are shown in the Trumpet Design Parameters document in my folder.

Sight distance

• With a shoulder width of 12.5 feet and half a lane width (7.5 feet), we have adequate sight distance for the EB off-ramp according to HDM Figure 201.6.
• Sight distance was only calculated for the EB off-ramp. I don't think there will be anything within the EB on-ramp loop that will be an obstruction to sight distance. The WB off-ramp and WB on-ramp may have warehouses as a possible obstruction, but that’s only if they’re right next to the ramps.

Max # of lanes at ramp terminal

• A possibility is that the EB and WB off-ramps will meet and continue straight until a T-intersection with a local road. At this intersection, traffic can either turn left or turn right to head towards the warehouse. I think at this intersection there can be three lanes, either 1 left turn and 2 right turns, 2 left turns and 1 right turn, or 1 left turn, 1 right turn, and 1 for both left and right turns. The last option might be the best because it will accommodate for the wider turns of trucks in both directions.

• As far as the lengths, it’s can connect to a proposed road (see comment in Trumpet Design Parameters document), but one of the Caltrans concerns is that having the ramps meet an intersection so far from the freeway means that they likely will not be the ones to maintain it.

Ramp metering for on-ramps

• For the EB on-ramp, it will most likely be one lane for ramp metering since the space is already so tight as it is. For the WB on-ramp, we can have two lanes for ramp metering since space is not an issue.

[PPMN4]

Completed. Check "Alternative 4 HA v2.dgn" and "Alt 4 Horizontal Alignment" files in google drive folder "06 - Joint Design Teams -> 02 - Design Team 2 (Zi) -> Paul"

[Qhuynh1881]

Completed. Check "Alignment.dgn" files in google drive folder "06 - Joint Design Teams -> 01 - Design Team 1 (Dre) -> Personal -> 5. Quynh Huynh (Designer 4)"

[Mhn110]

Completed. Check "Alignment.dgn" files in google drive folder "06 - Joint Design Teams -> 01 - Design Team 1 (Dre) -> Personal -> 3. Matthew (Designer 3) -> DDI Interchange"