HCS Streets module implements an emissions model based on a research project which incorporates safety and environmental measures into signal optimization.
The emissions model was based on NGSIM Data, and pollutant outputs are calculated for urban segments as a function of Vehicle-MilesTravelled and the number of STOPS for vehicles. As a result, environmental measures benefit from both reductions in travel quantity and congestion/delay mitigation measures.
Multilane Highways Merge/Diverge and Weaving Segments
The HCM can analyze isolated merge, diverge, or weaving segments on multilane highways and C-D Roads.
On the HCS Freeways module, for isolated segment analysis, the option “Highway or C-D Roadway” is used to analyze ramps or weaving segments on multilane highways.
Note that other parameters, noticeably the FFS, must match those of multilane highways for the method to work consistently.
Delays for the Main Street at Two-Way Stop-Controlled Intersections
At two-way stop-controlled intersections, Rank 1 movements (main street through and right-turns) are free. When shared lanes are used, the left-turn movements (Rank 2) cause delays that may affect other main street movements.
The Streets module in HCS provides the user with two calculation modes. The Auto-Calculate option is set as the default option for Streets and recommended for most projects, updating all calculations automatically whenever any input is changed.
When the Auto-Calculate option is off, all model outputs, including Control Delay, Level of Service (LOS), and the final phasing/timing diagrams, are frozen and grayed out until the user pushes the button “Force Calculations,” as shown below. This option gives the user a higher degree of control when input changes are applied to the model, which can speed up the inputting process for larger projects and help track adjustments to the project’s operational performance.
Users can copy selected table data on HCS modules formatted report and paste it directly to Excel, allowing for in-house customization of reports by using the standard MS Windows CTRL+C and CTRL+V keys.
In the example shown above, signal timing results are copied over a preformatted spreadsheet which automatically generates additional graphs.
The HCS Streets module can model the impact of work zones on signal saturation flows and capacities based on the number of open lanes and approach width. Expected queues and delays are provided, and can support planning-level or cost-benefit analysis without the need for additional tools.
Compliant to HCM Chapter 6, Chapter 06 – HCM and Alternative Analysis Tools, several HCS modules warn the user when specific demand and geometry configurations should preferably be modeled in a microsimulation environment rather than HCM methods.
In the example shown, a signalized intersection with insufficient storage length for the EBL movement and long spillback was exported to TSIS-CORSIM using a one-click feature on the HCS Streets module, where it is possible to visualize the queue spillback reaching the upstream intersection.
In the Highway Capacity Manual (HCM), on-ramp analysis is more often associated with Freeway Merge segments. However, one case covered by the HCM deals with lane additions or drops for merges and diverges respectively.
In these cases, the Merge segment should be treated as a Basic Freeway segment with the appropriate number of lanes. The Highway Capacity Software Freeways Facilities module automatically identifies such situations, facilitating the user to model the facility while ensuring HCM compliant analysis.
All HCS modules include an information box tool to assist users in reviewing their inputs before analyzing results. The information box can be accessed through its button on the module interface or the reports. Three levels of messages are displayed, as shown in the example below:
ERROR: there is an issue with the input data, which prevents the methodology from providing valid results. WARNING: this warns users that HCS procedures will adjust some input data to comply with HCM or software requirements. Users may want to review their inputs, but results will still be produced. INFO: these messages provide additional information that might be useful. These include cases where default values are changed or optional inputs are used. Results are produced normally.
The message with the most critical level defines the color of the icon displayed on the interface. A Green icon means no warning or errors exist.
The “Recall Mode” options are used to control how phases are called on actuated signalized intersections in HCS:
Off: phases may be skipped in the absence of vehicular demand, resulting in average green times close to the minimum. Min: Service the phase at least until its minimum green interval times out. Max: Displays green indication for its maximum duration, similar to pre-timed control. Ped: Place a pedestrian call on the phase and then service the phase for at least the pedestrian walk and clear times.
If on-ramp vehicles are having trouble entering the mainline or if on-ramp vehicles are reaching the end of the acceleration lane, this can be handled by increasing the percentage of drivers who will cooperate with a merging vehicle. The default value is only 20%. This parameter works with the anticipatory lane change logic to allow vehicles to merge more smoothly.
As microsimulation is stochastic in nature, TSIS-CORSIM can quickly provide descriptive statistics for any model. By using the multi-run command, the user may run several replications of the model with randomly generated seeds.
TSIS-CORSIM can model shared lanes adjacent to exclusive turn pockets (A HCM limitation) by using the correct channelization settings.
For surface street links, Option 9 on the channelization window (All sensible movements) will allow right turns from the rightmost full lane even if there is a right-turn pocket. Similarly, left turns can take place from the leftmost full lane even if there is a left-turn pocket, as shown on the Westbound approach of the intersection in the figure.
The Find tool (Ctrl+F) in TSIS-CORSIM allows the user to quickly 1. On the map mode, find and navigate to the chosen node number 2. On the report screen, find and quickly jump to the desired label or value
#TSIS_CORSIM can model toll lanes with different settings: – Automatic vs manual booths – Plaza lane-changing logic – Free lanes – Temporary lane closures – Vehicle restriction on selected lanes – Animations and all lane-based MOEs available – May be used to represent other types of booths (ex.:facility entrances)
Lane blockages can be modeled in CORSIM in two different ways.
An HOV lane can be used to simulate a lane blockage by defining it as closed to all traffic. By opening the HOT lane to all traffic, CORSIM resumes normal operations.
Incidents are another way to simulate lane blockage. Incidents are specified in the first time period but can last longer than a time period. The max number of incidents for the entire simulation is 100, which can be spread out through the simulation as needed. Each subsequent incident can have different behavior, and parallel incidents can be modeled to represent, for example, a blockage in one lane and rubbernecking in adjacent lanes. Queuing information is obtained from detectors or upstream from the blockage.
TSIS 6.0 was originally released in January 2007. In the next three years, TSIS 6.1 and TSIS 6.2 introduced several improvements including TSIS Next interface, 9-lane NETSIM approaches, left-hand drive, new sample networks, signal pre-emption for actuated controllers, traffic assignment for actuated controllers, two-lane rural highways with passing and no-passing zones, vehicle type O-D volumes in FRESIM, animation plus input editing in TSIS Next, new sample networks.
The latest release of TSIS (TSIS 6.3) combined CORSIM and TRANSYT-7F signal optimization program in one product. Other updates included a new Streets Editor, HOT lanes, advanced toll plazas, interactive lane alignment in TSIS Next and adaptive cruise control.
The Highway Safety Manual can predict crashes for freeway speed-change lanes (entrance and exit points). It covers the area between the gore point and the taper point and includes vehicles in the speed-change lane or in the freeway lanes on the same side of the freeway as the speed-change lane, as shown in the figure.
Crash prediction models for Freeways were developed as part of the 2014 Supplement of the HSM and are already implemented in the Highway Safety Software.
The Empirical Bayes method can be used for correcting the regression-to-mean bias to the application of the Safety Performance Functions (SPFs). The Empirical Bayes Method consists of weighting the crash obtained by combining two sources: accident history and a safety prediction model.
Use Highway Safety Software – HSS to improve your estimation, as shown in the image.
According to the HSM, a Type B weaving section length is the gore-to-gore distance measured along the edge of the freeway. The gore point is where the pair of solid white pavement markings that separate the ramp from the freeway main lanes are 2 feet apart. If the markings do not extend to a point where they are 2.0 ft apart, then the gore point is found by extrapolating both markings until the extrapolated portion is 2.0 ft apart. If the measured gore-to-gore distance exceeds 0.85 mi (4,500 ft), then a weaving section is not considered to exist. Rather, the entrance ramp is a “lane add” and the exit ramp is a “lane drop.”
If you have a Type B weaving, make sure to check “Any Ramps within 0.5 mi” in HSS to enable weaving-related inputs.
The base condition for Safety Performance functions in a facility is the absence of lighting. Thus, nighttime effects on crashes are addressed in HSM/HSS through CMFs. It is possible to use calibrated proportions in Highway Safety Software to increase model accuracy.
According to HSM, the definition of an intersection crash varies between agencies. It can be considered an intersection crash that occurs within the intersection crosswalk limits or physical intersection area. Other agencies consider all crashes within a specified distance, such as 250 ft, from the center of an intersection to be intersection crashes. However, some crashes occurring within 250 ft of an intersection cannot be considered intersection crashes since some of these may have happened regardless of intersection existence. When evaluating conditions and seeking solutions, consideration should be given to these differences in definitions.