Control of Congestion in Highly Saturated Networks: Development of Signal Timings

This working paper is one in a series of four describing a study of the control of traffic congestion in a network of highly saturated signalised junctions in Bangkok. Other papers in the series are: WP 248: Survey Design and Data Collection 250: Incidents and their Management 251: Experimental Results and Conclusions The study itself was a follow-up to a previous study already reported in WP 220, WP 221 and WP 222

Control of Congestion in Highly Saturated Networks: Development of Signal Timings

This working paper is one in a series of four describing a study of the control of traffic congestion in a network of highly saturated signalised junctions in Bangkok. Other papers in the series are: WP 248: Survey Design and Data Collection 250: Incidents and their Management 251: Experimental Results and Conclusions The study itself was a follow-up to a previous study already reported in WP 220, WP 221 and WP 222

Pilot Survey – Queue Management Strategies for Urban Traffic Control Systems

BACKGROUND 1.1 Advances in traffic signal optimization have produced increases in the capacity of urban road networks, but recent growth in demand has meant that many junctions operate at or above saturation levels. Delay costs increase dramatically when queues extend to block upstream junctions and queue management strategies are now required to ensure that local traffic signals operate effectively when oversaturated conditions occur. 1.2 The aims of this SERC-funded "Queue Management Strategies" project are as follows: (a) To generalise the strategies for queue management that were developed and tested empirically in Bangkok (See ITS WP 249 and WP 251); (b) To develop a computer graphics model to represent queue propagation; (c) To test the strategies' applicability and performance in UK networks; (d) To investigate their incorporation into standard signal optimization programs

Control of Congestion in Highly Saturated Networks: Working Paper 251 – Experimental Results and Conclusions

This working paper describes the results and conclusions drawn from experiments in traffic control carried out in Bangkok, Thailand, during a study of the control of highly saturated networks. Other papers in the series are WP 248 (Survey Design and Data Collection) WP 249 (Development of Signal Timings) and WP 250 (Incidents and their Management) This study formed a follow-up to an earlier study reported in WP 220, WP 221 and WP 222

Control of Congestion in Highly Saturated Networks: Survey Design and Data Collection

This working paper describes the initial stages of a tlfollow-uptl study of the control of highly saturated signalised junctions in Bangkok. The previous study has been reported in WP 220, WP 221 and WP 222. This paper describes why particular junctions were chosen for this second study and reports on the results of a survey designed to produce the data input requirements for TRRL1s TRANSYT program. TRANSYT is a method of finding the "bestt1 fixed-time plans with which to co-ordinate the traffic signals in any network of roads for which the average traffic flows are known. While this paper deals with the data input requirements, such as average flows, the results of an experiment comparing TRANSYT recommended signal timings with Traffic Police control will be described in a subsequent paper (WP 251)

Control of Congestion in Highly Saturated Networks: Incidents and Their Management

This working paper is one in a series of four describing a study of the control of traffic congestion in a network of highly saturated signalised junctions in Bangkok. Other papers in the series are: WP 248: Survey Design of Data Collection 249: Development of Signal Timings 251: Experimental Results and Conclusions The study itself was a follow-up to a previous study already reported in WP 220, WP 221 and WP222

Queue Management Project: Testing Strategies Using the Model.

This Working Paper is one of a series representing work under an SERC grant on queue management strategies for urban traffic control systems whose objectives are:- (i)to generalise the strategies developed in an earlier study of queue management, (ii)to develop a computer graphics based representation of queue propagation and management; (iii)to test the strategies' applicability and performance in UK networks; (iv)to investigate their incorporation into standard signal optimisation programs. Clark (1991) in WP 343 describes the graphics model developed at ITS as a queue-management tool for traffic engineers. In order to calibrate the model, and later implement a suitable queue management strategy recommended by the model, a small oversaturated urban traffic network was required. Six possible sites in the West Yorkshire region were suggested by HETS (West Yorkshire Highway Engineering and Technical Services) for consideration. Wellington Street in Leeds city centre was identified as the most suitable being a linked series of three signalized junctions where blocking-back was commonplace, parking violations were minimal and an adequate filming position was available

Proton transfer reactions of N-aryl triazolium salts: unusual ortho-substituent effects

Previous studies of the C(3)-hydrogen/deuterium exchange reactions of the triazolium ion conjugate acids of triazolyl N-heterocyclic carbenes revealed a change of mechanism under acidic conditions with N1-protonation to a dicationic salt. Interestingly, the data suggested an increase in pKaN1 in the presence of a N-pentafluorophenyl substituent relative to other N-aryl substituents with hydrogens or methyl substituents rather than fluorines at the ortho-positions. To probe the presence of an apparent donor effect of a N-pentafluorophenyl substituent, which differs from the more common electron withdrawing effect of this group, we have studied the analogous deuterium exchange reactions of four triazolium salts with heteroatoms or heteroatom substituents in the 2-position and/or 6-position of the N-aryl ring. These include triazolium salts with N-2,4,6-tribromophenyl 11, N-2,6-dichlorophenyl 12, N-2-pyridyl 13 and N-2-pyrimidinyl 14 substituents. The log kex – pD profiles for 11, 12 and 14 were found to show similar trends at lower pDs as for the previously studied N-pentafluorophenyl triazolium salt, hence supporting the presence an apparent donor effect on pKaN1. Surprisingly, the log kex – pD profile for N-pyridyl salt 13 uniquely showed acid catalysis at lower pDs. We propose herein that this data is best explained by invoking an intramolecular general base role for the N-(2-pyridyl) substituent in conjunction with N1-protonation on the triazolium ring. Finally, the second order rate constants for deuteroxide ion catalysed C(3)-H/D exchange (kDO, M−1 s−1), which could be obtained from data at pDs >1.5, were used to provide estimates of C(3)-carbon acid pKaC3 values for the four triazolium salts 11, 12, 13, 14

The effect of different combinations of vascular, dependency and cognitive endpoints on the sample size required to detect a treatment effect in trials of treatments to improve outcome after lacunar and non-lacunar ischaemic stroke

Background Endpoints that are commonly used in trials of moderate/severe stroke may be less frequent in patients with minor, non-disabling stroke thus inflating sample sizes. We tested whether trial efficiency might be improved with composite endpoints. Methods We prospectively recruited patients with lacunar and minor non-lacunar ischaemic stroke (NIHSS ≤ 7) and assessed recurrent vascular events (stroke, transient ischaemic attack (TIA), ischemic heart disease (IHD)), modified Rankin Score (mRS) and cognitive testing with the Addenbrooke’s Cognitive Examination (ACE-R) one year post-stroke. For a potential secondary prevention randomised controlled trial (RCT), we estimated sample sizes using individual or combined outcomes, at power 80% (and 90%), alpha 5%, required to detect a relative 10% risk reduction. Results Amongst 264 patients (118 lacunar, 146 non-lacunar), at one year, 30/264 (11%) patients had a recurrent vascular event, 5 (2%) had died, 3 (1%) had clinically-diagnosed dementia, 53/264 (20%) had mRS ≥ 3 and 29/158 (19%) had ACE-R ≤ 82 (57 could not attend for cognitive testing). For a potential trial, at 80% power, using mRS ≥ 3 alone would require n > 5000 participants, recurrent vascular events alone n = 9908 participants, and a composite of any recurrent vascular event, ACE-R ≤ 82, dementia or mRS ≥ 2 (present in 56% of patients) n = 2224 patients. However, including cognition increased missing data. Results were similar for lacunar and non-lacunar minor ischaemic stroke. Conclusions Composite outcomes including vascular events, dependency, and cognition reduce sample size and increase efficiency, feasibility, and relevance to patients of RCTs in minor ischaemic stroke. Efficiency might be improved further with more practical cognitive test strategies